Systems and methods for enhancing blood circulation

ABSTRACT

A method for increasing circulation in a breathing person utilizes a valve system that is interfaced to the person&#39;s airway and is configured to decrease or prevent respiratory gas flow to the person&#39;s lungs during at least a portion of an inhalation event. The person is permitted to inhale and exhale through the valve system. During inhalation, the valve system functions to produce a vacuum within the thorax to increase blood flow back to the right heart of the person, thereby increasing cardiac output and blood circulation.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation in part application of U.S. patentapplication Ser. No. 10/119,203, filed Apr. 8, 2002, which is acontinuation in part application of U.S. patent application Ser. No.09/854,238, filed May 11, 2001 U.S. Pat No. 6,604,523; which is acontinuation in part application of U.S. patent application Ser. No.09/546,252, filed Apr. 10, 2000 now U.S. Pat No. 6,526,973, which is acontinuation of U.S. patent application Ser. No. 08/950,702, filed Oct.15, 1997 (now U.S. Pat. No. 6,062,219), which is a continuation-in-partapplication of U.S. patent application Ser. No. 08/403,009, filed Mar.10, 1995 (now U.S. Pat. No. 5,692,498), which is a continuation-in-partapplication of U.S. patent application Ser. No. 08/149,204, filed Nov.9, 1993 (now U.S. Pat. No. 5,551,420), the disclosures of which areherein incorporated by reference.

This application is also related to U.S. application Ser. No. 09/967029,filed Sep. 28, 2001, the complete disclosure of which is hereinincorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to devices and methods used inconjunction with increasing blood circulation. In particular, thepresent invention relates to devices and methods for increasing bloodcirculation in spontaneously breathing individuals.

Many individuals have a need to increase their blood circulation. Thiscan be the case even if the person is considered to have normal bloodcirculation. One obvious way to increase blood circulation is toparticipate in physical activity, such as running, walking, swimming andthe like. However, participation in such activities may be inconvenient,and in some cases unpractical or altogether impossible.

Hence, this invention is related to alternative techniques forincreasing blood circulation.

BRIEF SUMMARY OF THE INVENTION

In one embodiment, the invention provides a method for increasingcirculation in a breathing person. According to the method, a valvesystem is interfaced to the person's airway and is configured todecrease or prevent respiratory gas flow to the person's lungs during atleast a portion of an inhalation event. The person is permitted toinhale and exhale through the valve system. During inhalation, the valvesystem functions to produce a vacuum within the thorax to increase bloodflow back to the right heart of the person, thereby increasing cardiacoutput and blood circulation. More specifically, coupling of the valvesystem to a breathing person increases the magnitude and prolongs theduration of negative intrathoracic pressure in the person's chest, i.e.,increases the duration and degree that the intrathoracic pressure isbelow or negative with respect to the pressure in the peripheral venousvasculature to increase venous return. By enhancing the amount of venousblood flow into the heart and lungs (since equilibration ofintrathoracic pressure during inhalation occurs to a greater extent fromenhanced venous return rather than rapid inflow of gases into the chestvia the patient's airway) cardiopulmonary circulation is increased.

In one aspect, the valve system is incorporated into a facial mask thatis coupled to the person's face. In another aspect, the valve systemincludes a pressure responsive inflow valve that may have an actuatingpressure in the range from about 0 cm H₂O to about −40 cm H₂O.Conveniently, the actuating pressure of the valve may be varied overtime.

In one particular aspect, the valve system may also be configured toprevent or decrease exhaled gases from exiting the person's lungs duringat least a portion of an exhalation event to further increase bloodcirculation. To increase the circulation, the valve system may beinterfaced for a time period in the range from about 30 seconds to about24 hours. In a further aspect, a supply of oxygen may be added throughthe valve system to supplement oxygen delivery to the person. The valvesystem also functions to deliver this oxygen into the blood byincreasing circulation through the lungs, and also increasing tidalvolume (the amount of gas that enters the lungs with each breath).

Such a method may also be used to treat various diseases, such asdiseases that are related to impaired venous blood flow or from poorblood circulation. Examples of such conditions that may be treated usingsuch techniques include venous stasis ulcers, deep vein thrombosis,wound healing, and lymphedema. The invention may also be used to treatrenal failure.

In a specific embodiment, impeding the airflow into the patient's lungsis accomplished by the use of a flow restrictive or limiting member,such as a flow restrictive orifice disposed within or connected inseries with a lumen of a ventilation tube, or a pressure-responsivevalve within a lumen of the tube to impede the inflow of air. Thepressure-responsive valve is biased to open to permit the inflow of airwhen the intrathoracic pressure falls below a threshold level. In orderto properly ventilate the patient, the method may permit the injectionof respiratory gases. When periodic ventilation is performed, gases canbe delivered either through the impeding step or in another embodimentthey can bypass the impeding step. In some cases, an oxygen enriched gasmay be supplied to the patient through the pressure-responsive valveonce this valve opens.

A specific embodiment further provides means for impeding air fromleaving the lungs during exhalation to further enhance cardiopulmonarycirculation by enhancing positive intrathoracic pressure.

An apparatus for enhancing cardiopulmonary circulation according to oneembodiment may comprise an improved endotracheal tube having a flowrestrictive element for impeding airflow from the patient's lungs duringchest inhalation. A second apparatus according to the invention providesfor an improved air-delivery system comprising a compressible structurehaving a flow restrictive element included in or attached to an openingof the compressible structure to impede the flow of gases to thepatient's lungs. Also, a connector is provided for interfacing thecompressible structure to the patient, preferably by attaching a facialmask or endotracheal tube to the structure. Alternatively, a mouth piecemay be coupled to the valving system.

In another aspect of the invention, a valving system is provided forregulating airflow into a patient's lungs when breathing. The systemincludes a housing having an upstream region and a downstream region. Ameans is provided between the upstream region and the downstream regionfor inhibiting air from flowing from the upstream region to thedownstream region when the pressure in the downstream region is lessthan the pressure in the upstream region. In this manner, air isinhibited from flowing into the patient's lungs during an inhalationattempt thereby forcing more venous blood into the chest and enhancingvital organ perfusion. A means is further provided for allowing air toflow into the downstream region when ventilating the patient. In thisway, adequate ventilation can be provided to the patient during theprocedure.

In one particular aspect, the inhibiting means comprises a valve whichinhibits airflow from the upstream region to the downstream region whenthe pressure in the downstream region is less than the pressure in theupstream region. The valve preferably includes a diaphragm which isclosed when the pressure in the downstream region is less than or equalto the pressure in the upstream region. Such a configuration preventsair from flowing into the patient's lungs during an attempted inhalationwhile allowing air to be exhausted from the patient's lungs duringexhalation. Preferably, the diaphragm is constructed of a flexiblemembrane. Alternatively, the diaphragm can be constructed using a ball.

In another particular aspect, the diaphragm is biased to open when thepressure in the downstream region is about 2 cm H₂O or greater, and morepreferably at about 2 cm H₂O to 10 cm H₂O. Biasing of the diaphragm inthis manner increases intrathoracic pressure during exhalation tofurther enhance vital organ perfusion.

In still a further aspect, the means for allowing air into thedownstream region includes a means for opening the diaphragm when air isinjected into the upstream region to ventilate the patient. The meansfor opening the diaphragm preferably includes an ambient pressure regionthat is adjacent the diaphragm. When air is injected into the upstreamregion, the pressure within the upstream region increases therebydrawing the diaphragm into the ambient pressure region and allowing theair to flow to the patient's lungs.

In an alternative aspect, the means for allowing air into the downstreamregion comprises a pressure-responsive valve at the downstream region.The pressure-responsive valve allows air into the downstream region whenthe pressure in the downstream region falls below a threshold level,usually in the range from 0 cm H₂O to −40 cm H₂O. Thepressure-responsive valve is advantageous in allowing ventilation to beprovided to the patient while still employing the diaphragm to enhancethe extent and duration of negative intrathoracic pressure. Examples ofpressure-responsive valves that may be used include, for example, aspring biased valve, an electromagnetically driven valve, or a valveconstructed of any deflectable material that will deflect when thethreshold pressure is exceeded. As one specific example, the valve maybe constructed of a magnetically charged piece of material with a narrowtolerance that is attracted to a gate. This valve will open when themagnetically charged gate pressure is exceeded. In this way, when thenegative intrathoracic pressure is exceeded, the valve will be pulledaway from the gate to permit gases to flow to the lungs. Such a valvecould also be used in place of the diaphragm valve discussed above.

In one option, a source of oxygen-enriched gas may be coupled to thepressure-responsive valve to supply an oxygen-enriched gas to thepatient when the pressure-responsive valve is opened. A regulator may beemployed to regulate the pressure and/or flow rate of the gas. Forexample, the pressure may be regulated to be less than the actuatingpressure of the valve so that the pressurized gas will not flow to thepatient's lungs until the valve is opened when the negativeintrathoracic pressure is exceeded.

The system of the invention in another aspect is provided with an airexhaust opening in the housing at the upstream region for exhausting airfrom the housing. A valve is provided in the exhaust opening whichinhibits air from flowing into the housing through the exhaust opening.In this manner, air exhausted from the patient is in turn exhausted fromthe housing through the exhaust opening. In a further aspect, means areprovided for preventing air from exiting the housing through the exhaustopening during injection of air into the housing when ventilating thepatient. Preferably air is injected into the housing from a respiratorydevice, such as a respiratory bag, a ventilator, or the like.

In still a further aspect of the invention, an endotracheal tube, asealed facial mask, a laryngeal mask, or other airway tube, mouthpiece,or the like is provided and is connected to the housing at thedownstream region for attachment to the patient. The endotracheal tubeor like device is for insertion into the patient's airway and provides aconvenient attachment for the valving system to the patient.

In one embodiment, the invention provides a mechanism to vary theactuating pressure of the inflow valve. In this way, a person is able tooperate the mechanism to vary the impedance. In some cases, the valvesystems of the invention may include a pressure gauge to display theintrathoracic pressures. By having this information readily available,the user has more information to assist in setting the desired actuatingpressure of the inflow valve.

In one aspect, the varying mechanism is configured to vary the actuatingpressure to a pressure within the range from about 0 cm H20 to about −40cm H20. In another aspect, the inflow valve comprises a shaft having aseal that is configured to block an opening in the housing, and a springthat biases the seal against the housing. With such a configuration, themechanism may comprise a knob that is movable to vary the biasing forceof the spring. For example, the knob may be rotatably coupled to theshaft so that the user may simply turn the knob to vary the actuatingpressure.

In another embodiment, the valve systems of the invention may beprovided with a safety ventilation passage. If the valve system isinappropriately applied to a patient who is spontaneously breathing, thepatient may breathe through this passage while the valve system iscoupled to the patient's airway. A safety mechanism is used to maintainthe safety ventilation passageway open to permit respiratory gases tofreely flow to the patient's lungs until actuated by a rescuer to closethe safety ventilation passageway. With such an arrangement, the patientis able to freely breathe if they are capable of so doing.

In one aspect, the safety ventilation passageway is provided through theinflow valve when the inflow valve is in an open position. With thisconfiguration, the safety mechanism is configured to maintain the inflowvalve in the open position until actuated by the user to move the inflowvalve to a closed position. A variety of ways may be used to actuate thesafety mechanism. For example, the housing may include a ventilationport to permit respiratory gases to be injected into the housing, andthe safety mechanism may comprise a sensor to sense when the rescuerinjects respiratory gases into the housing. In one embodiment, a signalfrom the sensor is used by a control system to move the inflow valvefrom the open position to the closed position. As an example, the sensormay be movable upon injection of respiratory gases into the housing, andthe control system may comprise a set of gears that are coupled to thesensor and a cam that is movable by the gears to close the inflow valve.Alternatively, the control system may comprise an electronic controller,a solenoid and a cam. This mechanism may be configured to takeelectrical signals from the sensor and to operate the solenoid to movethe cam and thereby close the inflow valve. As another example, a flapmay be moved upon injection of the gases. The flap may cause themovement of a variety of mechanical components that physically reset theinflow valve to the closed position.

A variety of sensors may be used to sense injection of the respiratorygases. For example, sensors that may be used include electronic switchesthat move in a gas stream, thermistors to sense temperature changes, CO₂detectors, materials that experience a change of resistance when flexed,mechanical flaps that move in a gas stream, and the like.

The invention also provides methods for increasing the blood pressure ina spontaneously breathing person. According to the method, an inflowvalve is coupled to the person's airway and the person inhales andexhales. During inhalation, the inflow valve inhibits or completelyprevents respiratory gases from entering the lungs for at least sometime to augment the person's negative intrathoracic pressure and therebyassist in increasing blood flow back to the right heart of the person.In so doing, the person's blood pressure is enhanced. The resistance oractuating pressure of the inflow valve may be based on one or moresensed physiological parameters. For example, one parameter may be thenegative intrathoracic pressure. For instance, the inflow valve may beused to achieve a negative intrathoracic pressure in the range fromabout 0 cm H20 to −50 cm H20 for flow rates in the range from about zeroflow to about 70 liters per minute. Other parameters that may be sensedinclude respiratory rate, end tidal CO₂, tissue CO₂ content, positiveend expiratory pressure, blood pressure and oxygen saturation. Theseparameters may be used individually or in combination when adjusting theresistance of the inflow valve. For example, even if the sensed negativeintrathoracic pressure is within a desired range, the end tidal CO₂ maybe outside of a desired range. As such, the resistance of the valve maybe adjusted until the end tidal CO₂ is acceptable. Conveniently, theinflow valve may be manually operated or operated in an automatedfashion. For example, a controller may be used to receive the sensedparameters and then to send signals to an adjustment mechanism thatoperates the valve to vary the resistance or actuating pressure.

Such a process may be used to treat a variety of conditions where theperson's blood pressure is low. For example, such a procedure may beused where the person has low blood pressure due to blood loss, due tothe administration of a drug, due to a high gravitational state, due tovasodepressor syncope, due to drowning, due to heat stroke, due to heartattack, due to hypothermia, due to right heart failure, after a returnto earth from space, due to sepsis, pericardial effusion, cardiactamponade, or the like.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating thoracic pressure changes over time whencompressing and decompressing a patient's chest according to the presentinvention.

FIG. 2A is a schematic view illustrating airflow through a ventilationcircuit when compressing a patient's chest according to the presentinvention.

FIG. 2B is a schematic view illustrating airflow through a ventilationcircuit when decompressing a patient's chest according to the presentinvention.

FIG. 3 is a schematic illustration of a first alternative embodiment ofa device for impeding airflow into a patient's lungs according to thepresent invention.

FIG. 4A is a schematic illustration of a second alternative embodimentof the device for impeding airflow into a patient's lungs according tothe present invention.

FIG. 4B is a schematic illustration of the device in FIG. 4A with acommon inhalation/exhalation port.

FIG. 5A is a schematic view of a one-way valve used in the device forimpeding airflow according to the present invention.

FIG. 5B is a schematic view of the one-way valve in FIG. 5A that is heldopen.

FIG. 5C is a schematic view of a one-way valve that is closed until athreshold pressure is present in the tube according to the presentinvention.

FIG. 6A is a schematic view of a spring biased inflow valve and a springbiased expiration valve to be used in accordance with the presentinvention.

FIG. 6B is a schematic view of FIG. 6A showing the operation of thevalves during outflow of air.

FIG. 6C is a schematic view of FIG. 6A showing the operation of thevalves during inflow of air.

FIG. 7 is a schematic view of a single valve that is spring biased fromboth sides to be used as an inflow valve and an expiration valveaccording to the present invention.

FIG. 8 is a schematic view of a flow restricting orifice to be used witha flow restrictive device according to the present invention.

FIG. 9 is a schematic view of an exemplary embodiment of the device forimpeding airflow into a patient's lungs according to the presentinvention.

FIGS. 10A-10C are schematic views illustrating another embodiment of thepresent invention allowing for periodic patient ventilation through abypassing valve.

FIG. 11 is a schematic view of an exemplary valving system forregulating airflow into a patient's lungs according to the presentinvention. The valving system is shown with air being exhausted from apatient's lungs.

FIG. 12 illustrates the valving system of FIG. 11 during decompressionor resting of the patient's chest.

FIG. 13 illustrates the valving system of FIG. 11 with apressure-responsive valve being opened when the negative intrathoracicpressure in the patient's chest exceeds a threshold amount duringdecompression of the patient's chest.

FIG. 14 illustrates the valving system of FIG. 11 with a diaphragm beingopened during injection of air into the housing when ventilating thepatient.

FIG. 15 illustrates the valving system of FIG. 11 with a manuallyoperable valve being opened to allow air into the patient's lungs uponreturn of spontaneous circulation.

FIG. 16A is a cutaway side view of exemplary valving system according tothe present invention.

FIG. 16B is a top view of a deflector and a fenestrated mount of thevalving system of FIG. 16A.

FIG. 16C is an alternative embodiment of the valving system of FIG. 16A.

FIG. 16D illustrates the valving system of FIG. 16A with a source ofpressurized gas coupled to a pressure-responsive valve according to theinvention.

FIG. 17 is a schematic view of an alternative embodiment of a valvingsystem having a ball as a diaphragm.

FIG. 18 is a schematic view of a device for impeding air flow into thepatient's lungs and for providing air to the patient's lungs when neededfor ventilation.

FIG. 19 is a side view of one embodiment of a valving system having anadjustable pressure responsive valve according to the invention.

FIG. 20 is a cross sectional side view of the adjustable pressureresponsive valve of FIG. 19.

FIG. 21 is a top view of the valve of FIG. 20.

FIG. 22 illustrates the valve of FIG. 21 with a cap being removed.

FIG. 23 is a schematic side view of a safety mechanism for a valvingsystem that permits respiratory gases to freely flow to the patient'slungs through a ventilation passage according to the invention.

FIG. 24 illustrates the safety mechanism of FIG. 23 when actuated toprevent respiratory gases from flowing through the ventilation passage.

FIG. 25 is a schematic side view of a valving system having anintegrated safety mechanism that permits respiratory gases to freelyflow to the patient's lungs through an inflow valve according to theinvention.

FIG. 26 illustrates a flow sensor and lever arm of the safety mechanismof FIG. 25 prior to actuation by the rescuer.

FIG. 27 illustrates the valving system of FIG. 25 when the safetymechanism is actuated by the rescuer to closed the inflow valve.

FIG. 28 illustrates the flow sensor and lever arm of FIG. 26 whenactuated by the rescuer.

FIG. 29 is an end view of the valving system of FIG. 25.

FIG. 30 is a more detailed view of the inflow valve of FIG. 25 when inthe open position.

FIG. 31 illustrates the inflow valve of FIG. 30 when in the closedposition.

FIG. 32 is a side schematic view of one embodiment of a safety valveshown in a closed position according to the invention.

FIG. 33 illustrates the safety valve of FIG. 32 in an open position.

FIG. 34 is a side schematic view of another embodiment of a safety valveshown in a closed position according to the invention.

FIG. 35 illustrates the safety valve of FIG. 34 in an open position.

FIG. 36 is a side schematic view of yet another embodiment of a safetyvalve shown in a closed position according to the invention.

FIG. 37 illustrates the safety valve of FIG. 36 in an open position.

FIG. 38 is a schematic side view of an embodiment of a valving systemhaving a safety valve that is in a closed position according to theinvention.

FIG. 39 illustrates the valving system of FIG. 38 when the safety valveis moved to the open position during a gasp by a patient.

FIG. 40 illustrates the valving system of FIG. 38 during ventilationwhich causes the safety valve to move back to the closed position.

FIG. 41 is a schematic diagram of a valving system having a pressuregauge to measure pressures within the valving system according to theinvention.

FIG. 42 is a cross-sectional schematic view of one embodiment of asystem for treating a breathing person who is in shock according to theinvention.

FIG. 43 is top schematic view of the system of FIG. 42.

FIG. 44 illustrates the system of FIG. 42 when the person is inspiring.

FIG. 45 illustrates the system of FIG. 42 when the person is exhaling.

FIG. 46A illustrates one embodiment of an inflow valve according to theinvention.

FIG. 46B illustrates the inflow valve of FIG. 46A when the resistance toflow has been increased.

FIG. 47A illustrates another embodiment of an inflow valve according tothe invention.

FIG. 47B illustrates the inflow valve of FIG. 47A when a disk has beenmoved to increase flow resistance according to the invention.

FIG. 48A illustrates yet another embodiment of an inflow valve accordingto the invention.

FIG. 48B illustrates the inflow valve of FIG. 48A when a disk has beenrotated to increase resistance according to the invention.

FIG. 49A illustrates a further embodiment of an inflow valve accordingto the invention.

FIG. 49B illustrates the inflow valve of FIG. 49A when compressed toincrease flow resistance.

FIG. 50A illustrates yet another embodiment of an inflow valve accordingto the invention.

FIG. 50B illustrates the inflow valve of FIG. 50A when compressed toincrease flow resistance.

FIG. 51A illustrates a further embodiment of an inflow valve accordingto the invention.

FIG. 51B illustrates the inflow value of FIG. 51A when compressed toincrease flow resistance.

FIG. 52A illustrates still a further embodiment of an inflow valveaccording to the invention.

FIG. 52B illustrates iris mechanisms that have been operated to increasethe resistance to flow of the inflow valve of FIG. 52A.

FIG. 53A illustrates still a further embodiment of an inflow valveaccording to the invention.

FIG. 53B illustrates the inflow valve of FIG. 53A when a disk has beenpivoted to increase flow resistance.

FIGS. 54A through 54C illustrate one embodiment of a method for treatingshock according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, methods and devices for increasingcardiopulmonary circulation induced by spontaneous breathing areprovided. In particular, the invention improves blood circulation byproviding methods and devices which impede airflow into a patient'slungs to enhance negative intrathoracic pressure during attemptedinhalations, thus increasing the degree and duration of a pressuredifferential between the thorax (including the heart and lungs) and theperipheral venous vasculature. Enhancing negative intrathoracic pressurewith simultaneous impedance of movement of gases into the airway thusenhances venous blood flow into the heart and lungs and increasescardiopulmonary circulation.

In a broad sense, the present invention provides for occluding apatient's airway to prevent foreign (outside) air from flowing to apatient's lungs during attempted inhalations to enhance and sustain theduration of negative intrathoracic pressure and enhance bloodoxygenation and cardiopulmonary circulation. The patient's airway may beoccluded or inflow of gases impeded by any suitable device or mechanismsuch as by an endotracheal tube, a device attached to an endotrachealtube, a facial mask, a mouth piece used in mouth-to-mouth resuscitation,oropharyngeal airway, laryngeal mask airway, and the like.

A further aspect of the present invention provides for allowing impededair to flow into the patient's lungs during at least a portion of theinhalation attempt in order to provide some ventilation to the patientwhile still enhancing the extent and duration of negative intrathoracicpressure to enhance blood oxygenation. Impeding airflow to the patient'slungs may be accomplished by any flow restrictive element such as anorifice, a one-way valve, a spring biased or other valve which is set toopen when the negative intrathoracic pressure is in the range from about0 cm H₂O to −100 cm H₂O, and more preferably from about −3 cm H₂O toabout −40 cm H₂O. A valve designed to open at a threshold pressure valuemay be either fixed or variable, i.e., the pressure at which the valveopens may be adjusted or may be permanently fixed. Further, examples ofpressure-responsive valves that may be used include, for example, anelectromagnetically driven valve or a valve constructed of anydeflectable material that will deflect when the threshold pressure isexceeded. As one specific example, the valve may be constructed of amagnetically charged piece of material with a narrow tolerance that isattracted to a gate. This valve will open, i.e. separate from the gate,when the magnetically charged gate pressure is exceeded. In this way,when the negative intrathoracic pressure is exceeded, the valve will bepulled away from the gate to permit gases to flow to the lungs.

In some cases, a safety mechanism may be provided to permit respiratorygases to freely flow to the patient's lungs until the safety mechanismis actuated by the user. In this way, the valving system may be coupledto the patient but will only impede patient inspiration until actuatedby the user.

Another aspect of the invention provides for air to be impeded fromleaving the patient's lungs during exhalation to further enhancecardiopulmonary circulation by enhancing intrathoracic pressure.Typically, air is impeded from leaving the lungs during the exhalationwhen the positive intrathoracic pressure is in the range from about 2 cmH₂O to 50 cm H₂O, and more preferably from about 2 cm H₂O to about 20 cmH₂O. Valves that may be used to accomplish such a feature include, forexample, a spring valve, a diaphragm valve, include diaphragmsconstructed of silicone, and a magnetically charged plate that iscoupled to a gate. In this manner, when the positive pressure exceedsthe magnetic force, the plate is forced away from the gate to permit thegases to exit the lungs.

Another aspect of the present invention provides for ventilating orsupplying a gas to the patient. Ventilation of the patient in oneembodiment is performed at about every two to 20 inhalation andexhalation cycles, preferably twice every fifteen cycles, thus providingsufficient fresh air or other gases for adequate gas exchange with theblood in the lungs to the patient. Ventilating the patient may beaccomplished by any device or method suitable such as by a compressibleor collapsible structure, by a ventilatory bag such as the AMBU bagavailable from AMBU, Copenhagen, Denmark, or the like. Ventilation couldalso be superimposed on the exhalation phase to further augment positiveintrathoracic pressure. Furthermore, periodic ventilation could beperformed either through the impeding step or by bypassing the impedingstep altogether.

In an alternative embodiment, ventilation may be provided by introducingoxygen-enriched respiratory gases through the pressure-responsive valvethat permits gases into the lungs during the inhalation step once acertain threshold negative intrathoracic pressure is exceeded. Thiscould be introduced under pressure or at atmospheric pressure In thisway, during each inhalation, respiratory gases may be supplied to thelungs to ventilate the patient. Use of a pressurized gas is advantageousin that more respiratory gases may be supplied to the lungs once thepressure responsive valve opens. The pressurized gas may be supplied byconnecting a pressurized gas source, such as a pressurized tank or bagof O₂, to the back side of the pressure-responsive valve using a lengthof tubing. Conveniently, a regulator may be positioned between thepressure source and the valve to regulate the pressure and/or flow rateof the gas supplied from the pressure source. The pressure may beregulated such that it is less than the actuating pressure of the valve,e.g. by about 1 to 3 cm H₂O, so that the valve will not prematurelyopen. For example, if respiratory gases are to be supplied to thepatient when the negative intrathoracic pressure exceeds −14 cm H₂O, thepressure of the gas from the gas source must be set to less than 14 cmH₂O.

One advantage of supplying supplemental oxygen through the valve andinto the respiratory circuit is that addition of the supplemental oxygenmay more efficiently be placed into the blood stream. This is becausethe valve helps to increase blood circulation through the lungs tofacilitate the incorporation of additional oxygen into the lungs.Moreover, by injecting oxygen into the lungs, the tidal volume isincreased so that additional oxygen may be fed into the blood stream. Inone particular embodiment, such a configuration may be incorporated intoa diving mask so that a diver may incorporate more oxygen into the bloodwith a limited amount of oxygen (i.e., a tank of oxygen). Hence, theavailable oxygen may be better utilized, with less waste with eachbreath.

When ventilating a patient, the valves of the invention may be modifiedto regulate the flow rate of air into the lungs. This may beaccomplished for example, by including a flow regulator, valve,restriction, reduced size orifice or the like within or associated withthe valve so that as respiratory gases are injected into the valve,their flow rate is limited below a threshold amount as the gases enterthe patient's airway. By regulating the flow rate of injectedrespiratory gases, the pressure on the esophagus may be kept withincertain limits to prevent gastronomic distention. For example, a reducedsize orifice may be provided at or near the exit opening of the valvesystem housing to regulate the gas flow rate before the gases enter thepatient's airway. In this way, a technique is provided to ensure thatsubstantially all of the injected respiratory gases enter the patient'slungs.

One significant advantage of the invention is the ability to increase aperson's blood pressure. By interfacing the valving systems of theinvention with spontaneously breathing patients, the valving systems areable to increase the negative intrathoracic pressure when the personinhales. By so doing, more blood is returned to the right heart, therebyincreasing the person's blood pressure. The valving systems used toincrease the person's blood pressure may initially completely preventgas flow to the lungs during an inspiratory effort, or provide somemeasure of resistance. The complete prevention or initial resistance maybe adjusted sometime during the breathing maneuver so that gas flow mayproceed to the person's lungs for at least a portion of the inspiratorycycle. For example, if using a pressure responsive valve, the valve maybe set to open when reaching a pressure in the range from about 0 cm H₂Oto about −50 cm H₂O, more preferably from about 0 cm H₂O to about −20 cmH₂O, and most preferably from about −5 cm H₂O to about −15 cm H₂O forflow rates of about zero flow to about 70 liters per minute. For valvesthat simply provide resistance, the valve may be configured to providesimilar resistances during the inspiratory effort. Further, one or moresensors may be used to sense various physiological parameters and may beused to manually or automatically vary the cracking pressure of thevalve or the amount of resistance produced by the valve.

Examples of situations where the valving systems of the invention may beused to increase blood pressure include those where a spontaneouslybreathing patient has experienced blood loss, or after receiving a drug(including an anesthetic agent) that causes a decrease in bloodpressure. Patients with low blood pressure often suffer frominsufficient blood returning to the heart after each beat. This resultsin a decrease in forward blood flow out of the heart and eventually tolow blood pressure. By interfacing the valving systems to the airway,the amount of venous return to the right heart is increased to increaseblood pressure. Another example is where a spontaneously breathingpatient is in shock secondary to profound blood loss and needs increasedblood flow to the right heart. As a further example, such techniques maybe used with pilots or astronauts to increase blood flow back to theright heart in high gravitational states or when returning to earthafter space flight, and in patients who suffer from a rapid decrease inblood pressure due to vasovagal or vasodepressor syncope. Furtherexamples include low blood pressure due to heat stroke, drowning, heartattack, right heart failure, sepsis, pericardial effusion, tamponade, orthe like.

The valving systems of the invention may also incorporate or beassociated with sensors that are used to detect changes in intrathoracicpressures or other physiological parameters. Any of the sensorsdescribed herein may be configured to wirelessly transmit their measuredsignals to a remote receiver that is in communication with a controller.In turn the controller may use the measured signals to vary operation ofthe valve systems described herein. For example, sensors may be used tosense blood pressure, pressures within the heart, or the like and towirelessly transmit this information to a receiver. This information maythen be used by a controller to control the actuating pressure or theresistance of an inflow valve, to control the actuating pressure orresistance of an expiratory valve, to control the injection of oxygen orother gases, to control the administration of drugs or medications, orthe like.

The valve systems and/or facial masks of the invention may also includeone or more ports for the administration of drugs or other medicamentsto the patient's respiratory system. For example, ports may be providedfor injecting medicaments by a syringe or pressurized canister. Asanother example, a nebulized liquid medicament may be supplied throughsuch a port. As a further example, a powdered medicament may be suppliedthrough such a port.

Another feature of the invention is that it may be used to decreaseintracranial pressures that often result from trauma to the head. Bydecreasing intrathoracic pressures using the valve systems andtechniques of the invention, the resistance of venous return from thebrain to the heart is decreased. As such, more venous blood may beremoved from the brain, thereby decreasing intracranial pressures. Forexample, any of the valve systems of the invention may be coupled to thepatient's airway so that as the patient breathes, the negativeintrathoracic pressures generated by the patient are augmented to drawvenous blood out of the brain.

Referring now to FIG. 1, a graph illustrating thoracic pressure changesover time when compressing and decompressing the patient's chest isshown. Area 10 represents the amount of thoracic pressure during thecompression phase of active compression-decompression CPR (ACD-CPR).Cross-hatched area 12 represents the negative thoracic pressure duringthe decompression step of ACD-CPR without a flow restrictive means torestrict the flow of air into the patient's lungs. Double cross-hatchedarea 14 represents the increase in negative thoracic pressure when thepatient's airway is occluded according to the present invention duringthe decompression step of ACD-CPR. The significance of the increase innegative intrathoracic pressure during the decompression step is thatmore venous blood is forced into the chest from the peripheral venousvasculature. Consequently, more blood is allowed to be oxygenated andmore blood is forced out of the chest during the next compression. Asimilar scenario is provided when the person is spontaneously breathingand the airway is occluded.

In the embodiments that follow, various devices, systems and methods aredescribed for enhancing the negative intrathoracic pressure in order toincrease circulation. Although primarily described in the context ofCPR, it will be appreciated that such devices, systems and techniquesmay also be used for individuals that are spontaneously breathing and donot require the performance of CPR. Such individuals may or may not besuffering from any specific type of disease or ailment, but simply havea need for increased blood circulation (even with individuals havingnormal blood circulation). However, such techniques may be used forvarious diseases or ailments associated with blood circulation. Forexample, the invention may be used in cases related to impaired venousblood flow, such as venous stasis ulcers, deep vein thrombosis, woundhealing, and lymphedema. Another example is mild/moderate renal failure.

Hence, the invention may function as a patent powered pump that iscapable of enhancing venous return and increasing cardiac output innormal patents and well as those suffering from diseases. In embodimentsdescribed in connection with CPR (such as when the chest is compressedand decompressed), it will be appreciated that exhalation and inhalation(respectively) are analogous steps for spontaneously breathingindividuals. For convenience of discussion, some embodiments will onlybe described in connection with CPR, with the understanding that suchembodiments may also be used in connection with spontaneously breathingsubjects as well. Further, other types of valve systems may also be usedto increase blood circulation in breathing subjects, such as thosedescribed in copending U.S. application Ser. No. 09/966,945, filed Sep.28, 2001; and Ser. No. 09/967,029, filed Sep. 28, 2001, the completedisclosures of which are herein incorporated by reference.

In an exemplary embodiment, airflow may be impeded to the patient'slungs during inhalation by placing a ventilatory mask over the patient'smouth and nose. The ventilatory mask also has a pressure-responsivevalve attached to prevent airflow to the patient's lungs until thenegative intrathoracic pressure of the patient reaches a thresholdamount. Also attached to the mask and the pressure-responsive valve is aventilatory source to provide ventilation to the patient. Theventilatory source may be any device or apparatus suitable for properlyventilating the patient. Preferably, the ventilation source will be anAMBU bag. When ventilation is needed, the AMBU bag may be squeezed toforce air into the patient's lungs. The AMBU bag is described in U.S.Pat. No. 5,163,424 which is incorporated herein by reference.

In an alternative embodiment, a ventilation source, preferably an AMBUbag, is used in connection with an improved endotracheal tube. Apressure-responsive valve or other flow restrictive element is placedbetween the AMBU bag and the endotracheal tube. Preferably, the valvewill be positioned within a tube that connects the AMBU bag to theendotracheal tube. The combination of the endotracheal tube with theAMBU bag with adapter can be included in the definition of a“ventilation tube.” Before ACD-CPR is performed on the patient, theendotracheal tube is placed in the patient's trachea. Duringdecompression of the patient's chest, the valve prevents airflow to thepatient's lungs until the intrathoracic pressure reaches a thresholdamount. Additionally, the AMBU bag may be used to ventilate the patientat a desired time. Also included in this embodiment is a one-wayexpiration valve. This valve allows for expiration of air from thepatient during the compression step.

In a modification of either of the first two embodiments, apressure-responsive expiration valve may also be inserted between theAMBU bag (or comparable ventilation source) and the mask or endotrachealtube. This valve works in a similar manner to the pressure-responsivevalve which restricts airflow into the patient's lungs. However, thepressure-responsive expiration valve restricts airflow from thepatient's lungs during the compression step of ACD-CPR. An equivalentvalve is a positive end-expiratory pressure (PEEP) valve available fromAMBU International, Copenhagen, Denmark. Use of such anpressure-responsive expiration valve during inhalation may furtherincrease intrathoracic pressure and thereby force more blood out of thethorax.

In another alternative embodiment, an improved endotracheal tube is usedto restrict airflow into the patient's lungs during the activedecompression step. Included in the endotracheal tube is a flowrestrictive element which operates to impede air from flowing into thepatient's lungs. When the endotracheal tube is inserted into thepatient's trachea and the patient's chest is actively decompressed, theflow restrictive element impedes air from flowing to the patient's lungsslowing the rise in intrathoracic pressure and thus enhancing bloodoxygenation.

When using the improved endotracheal tube during ACD-CPR, periodicventilation of the patient will usually still be performed to enhancegas exchange to the patient. With the improved endotracheal tube, suchmanual ventilation may be accomplished by placing a ventilation sourceat the opening of the endotracheal tube to force oxygen through theendotracheal tube and into the patient's lungs.

Referring now to FIG. 2A, a schematic view illustrating airflow througha ventilation circuit 20 when compressing a patient's chest according tothe present invention is shown. During ACD-CPR, the chest is activelycompressed forcing air out of the lungs. This air is allowed to expirethrough a one-way expiration valve 22 within a ventilation circuit 20.

Referring now to FIG. 2B, the same schematic is shown illustratingairflow through the ventilation circuit 20 when decompressing thepatient's chest. When the patient's chest is actively decompressed, anegative intrathoracic pressure is created. When this pressure reaches athreshold amount, the inflow valve 24 will open causing air to flowthrough the ventilation circuit 20 into the patient's lungs. Air isallowed into the ventilation circuit 20 through a ventilation valve 26and into a ventilation bag 28. From the ventilation bag 28, the airpasses through the inflow valve 24 when the negative intrathoracicpressure reaches the threshold amount. The ventilation bag 28 is alsoused to manually ventilate the patient during ACD-CPR as required.

The method as discussed in connection with FIGS. 2A and 2B requires thechest to be compressed in the range from about 3.5 cm to 5 cm percompression and at a rate from about 60 to 100 compressions per minutefor adults.

Referring now to FIG. 3, a schematic illustration of a first alternativeembodiment of a device 35 for impeding airflow into a patient's lungsaccording to the present invention is shown. The device 35 comprises anendotracheal tube 36 which is placed into the patient's trachea andprovides a ventilation passageway. Connected to the endotracheal tube 36is a transition tube 38 which connects the endotracheal tube 36 to theventilation bag 28. Although the endotracheal tube 36 is shown connectedto the ventilation bag 28, the endotracheal tube 36 can be used alone orin connection with the ventilation bag 28. The ventilation bag 28 cancomprise any type of ventilation source capable of ventilating thepatient such as a compressible or collapsible structure. Preferably, theventilation bag 28 consists of an AMBU bag. Attached or connected to theend of the ventilation bag 28 is a one-way ventilation valve 26. Theventilation valve 26 serves to introduce air into the device 35.Attached or connected to the transition tube 38 is an inflowpressure-responsive valve 24. The inflow valve 24 is biased so that itopens when the negative intrathoracic pressure in the patient's chestreaches a threshold amount. As shown, only one inflow valve 24 isincluded in the device 35. However, the invention is not limited to onlyone inflow valve 24. Alternatively, a plurality of inflow valves 24could be connected in series along the ventilation tube 38. The inflowvalve 24 is also not limited to being connected in the center of thetransition tube 38, but may be positioned anywhere along the transitiontube 38. The inflow valve 24 could be permanently attached to theventilation bag 28 or transition tube 38 or could be detachable.Alternatively, the inflow valve 24 could be connected to the ventilationbag 28 itself or to the endotracheal tube 36.

The device 35 also contains a one-way expiration valve 22 which allowsfor air to be expired from the patient's lungs. This generally occursduring the compression phase of ACD-CPR. To insure that the air expiredfrom the patient's lungs will exit through the expiration valve 22, aone-way fish mouth valve 37 (the preferred valve) or any other type ofone-way valve can be placed between the inflow valve 24 and theexpiration valve 22. Alternatively, the inflow valve 24 itself may beconfigured as a one-way valve. In either case, air flowing from theendotracheal tube 36 toward the ventilation bag 28 will be forced toexpire through the expiration valve 22.

The device 35 may be further modified to include a pressure-responsiveexpiration valve 39 (not shown) located between the endotracheal tube 36and the transition tube 38. The pressure-responsive expiration valveworks in a reverse manner to that of the inflow valve 24. Specifically,the pressure-responsive expiration valve is biased so that during thecompression step of ACD-CPR, air will be allowed to expire from thepatient's lungs only when the intrathoracic pressure reaches a thresholdamount. The increase in intrathoracic pressure caused by thepressure-responsive expiration valve 39 during compression may assist inforcing more blood out of the thorax and reduce atelectasis of thelungs.

The purpose of the ventilation bag 28 is to provide ventilation to thepatient during ACD-CPR. When the ventilation bag 28 comprises an AMBUbag or similar bag used for ventilation, ventilation of the patient maybe performed by merely squeezing the AMBU bag with a human hand. Thisforces air to the patient's lungs as desired.

Referring to FIG. 4A, a second alternative embodiment of the device forimpeding airflow into a patient's lungs according to the presentinvention is shown. This particular embodiment is a modified andimproved endotracheal tube. Hence, the second alternative embodimentcomprises an endotracheal tube 36 having two lumens at its proximal end.The first lumen is an outflow lumen 40, and the second lumen is aninflow lumen 42. Located within outflow lumen 40 is a one-waypressure-responsive expiration valve 44 which operates in a mannersimilar to that discussed in connection with FIG. 3, except that theexpiration valve 44 is specifically designed as a one-way valve. Locatedwithin inflow lumen 42 is a one-way pressure-responsive inflow valve 45which operates to impede airflow to the lungs as discussed in connectionwith FIG. 3, except that the inflow valve 45 is also specificallydesigned as a one-way valve. Also shown in inflow lumen 42 and outflowlumen 40 is an O-ring 46 which will be discussed subsequently. Inflowvalve 45 and expiration valve 44 are designed as one-way valves so thatduring the compression phase, air can only be expired from the patientthrough the endotracheal tube 36 when the intrathoracic pressure reachesa threshold amount. At that moment, expiration valve 44 opens and airexpires from the patient through the outflow lumen 40. Duringdecompression, air cannot flow through the endotracheal tube 36 to thepatient's lungs until the negative intrathoracic pressure reaches athreshold amount. At that moment, inflow valve 45 opens allowing air toflow through inflow lumen 42 to the patient's lungs. Air is preventedfrom entering through the outflow lumen 40 because of the one-wayexpiration valve 44.

Ventilation is possible with the embodiment disclosed in FIGS. 4A and 4Bif the inflow lumen 42 is connected to a ventilation source such as aventilation bag. When the ventilation bag is squeezed, air is allowed toflow through the inflow lumen 42, through the endotracheal tube 36, andto the patient's lungs. In this embodiment, expiration valve 44 isdesigned so that during ventilation, expiration valve 44 will remaintemporarily closed preventing air flowing through inflow lumen 42 escapethrough outflow lumen 40.

FIG. 5A is a schematic view of a one-way inflow valve 45 used in adevice for impeding airflow according to the present invention. Theinflow valve 45 operates so as to allow air only to flow in onedirection. As shown, the spring biased inflow valve 45 is completelyopen. However, the invention also functions properly if the springbiased inflow valve 45 or the spring biased expiration valve 44 are notfully open. Upon successful completion of ACD-CPR, the O-ring 46 that ispositioned above the inflow valve 45 is repositioned so that inflowvalve 45 is held open as shown in FIG. 5B. Such a positioning of O-ring46 allows for unimpeded airflow to the patient once there is a return ofspontaneous circulation and the inflow valve 45 is no longer needed. AnO-ring 46 is also used in a similar manner to lock the one-wayexpiration valve 44 in an open position upon return of spontaneouscirculation. FIG. 5C illustrates the one-way inflow valve 45 in a closedposition. When closed, the inflow of air through the inflow valve 45 isoccluded.

FIG. 6A illustrates an inflow valve 47 that is spring biased and anexpiration valve 48 that is also spring biased. The inflow valve 47 andthe expiration valve 48 are connected in series and may be used in thefirst alternative embodiment as discussed in connection with FIG. 3, orwith the preferred embodiment discussed following in connection withFIG. 9. As shown in FIG. 6C, during the active decompression step, theinflow valve 47 is biased such that it will open when the negativeintrathoracic pressure reaches a threshold amount. During thecompression phase of ACD-CPR the expiration valve 48 will open to allowair to expire from the patient's lungs when the intrathoracic pressurewithin the patient's chest reaches a threshold amount as shown in FIG.6B. Since neither inflow valve 47 nor expiration valve 48 are one-wayvalves, a fish mouth valve 37 used in connection with a one-wayexpiration valve 22 as discussed in connection with FIG. 3 must be used.Other valves designed upon a similar principle as the fish mouth valvecombination with a one-way expiration valve could also be used. Only oneinflow valve 24 and one positive end pressure valve 44 are shown inFIGS. 6A-6C. However, a plurality of inflow valves 47 and/or expirationvalves 48 may be connected in a permanent or detachable manner in seriesto impede the inflow and outflow of air.

Although the valves in FIGS. 6A-6C are shown as being spring-biased, anyother valves designed upon a similar principle would work equally aswell. The use of such valves as disclosed in FIGS. 6A-6C is only oneembodiment and valves constructed according to various other methods andmaterials is also within the scope of the invention.

As shown in FIG. 7, the inflow valve 47 and the expiration valve 48 maybe combined into one joint valve 49 as shown. The joint valve 49 willoperate in a manner similar to the two valves 47 and 48 as described inconnection with FIG. 6.

FIG. 8 illustrates a flow restricting orifice 50 to be used to eitherimpede the airflow into or out of a patient's lungs. The flowrestricting orifice 50 operates so that during the decompression step ofACD-CPR airflow is impeded from entering into the patient's lungs, thusincreasing the negative intrathoracic pressure. During the compressionstep, the flow restricting orifice 50 operates to increase the thoracicpressure in the patient's chest by restricting air from existing fromthe patient's lungs.

FIG. 9 illustrates an exemplary embodiment for impeding airflow into apatient's lungs according to the present invention. As shown, the device51 comprises a ventilation bag 28 that is connected to a facial mask 52by an inflow valve 24 and an expiration valve 22. Although the facialmask 52 is shown connected to the ventilation bag 28, the facial mask 52can be used alone or in connection with the ventilation bag. Between theinflow valve 24 and the expiration valve 22 is a one-way fish mouthvalve 37 or any other type of one-way valve to prevent air from exitingthe patient's lungs and flowing to the ventilation bag 28. Theventilation bag 28 also contains a one-way ventilation valve 26 forallowing air to inflow into the device 51. The exemplary embodimentoperates in a manner similar to that of the first alternative embodimentas discussed in connection with FIG. 3. However, instead of inserting anendotracheal tube 36 into the patient's airway, the facial mask 52 isplaced over the patient's mouth and nose. A facial strap 54 (not shown)may also be wrapped around the head of the patient to secure theventilation mask 52 to the patient's face.

Device 51 is preferably used in connection with an oral airway device(not shown) to prevent the patient's airway from becoming occluded, e.g.by the patient's tongue. The oral airway device can be any device thatis used to keep the patient's tongue from slipping backward andoccluding the airway. Preferably, the oral airway device will be curvedand constructed of a plastic material and may or may not be attached tothe device 51.

During the decompression phase of ACD-CPR, air is prevented fromentering into the patient's lungs through the threshold inflow valve 24thus increasing the negative intrathoracic pressure. During thecompression phase, air is allowed to expire from the patient's lungsthrough the expiration valve 22. Also, the patient can be ventilatedduring ACD-CPR by manually squeezing the ventilation bag 28.Consequently, the preferred embodiment serves to enhance cardiopulmonarycirculation by increasing the negative intrathoracic pressure to forcemore blood into the chest from the peripheral venous vasculature.

FIGS. 10A-10C show another embodiment of the present invention whichallows the patient to be ventilated by bypassing the impeding step. Theembodiment comprises a ventilation tube 60 with a proximal end 62 and adistal end 64 that is connected to the patient. The ventilation tube 60has a one-way bypass valve 66 and a one-way pressure responsive valve68. The ventilation tube 60 may also have a manual switch 70 attached tothe bypass valve 66 and extending through a side of the ventilation tube60. As shown in FIG. 10A, the switch 70 may be set in a closed positionso that the one-way pressure responsive valve 68 opens when thethreshold pressure of the valve 68 has been exceeded. At this point, thevalve 68 opens allowing for ventilation of the patient. As shown in FIG.10B, the one-way pressure responsive valve 68 may be bypassed altogetherby manually placing the switch 70 in the open position so that thebypass valve 66 is opened allowing air to flow to the patient. FIG. 10Cillustrates the operation of the bypass valve 66 with the switch 70 inan inactive mode. Here, the rescuer performing ventilation may do sowithout added resistance from the impedance step as in FIG. 10A.Instead, bypass valve 66 opens only when the pressure at the proximalend of the tube 62 is greater than atmospheric pressure (0 mmHg),preferably in a range from about 0 mmHg to 5 mmHg. During decompressionof the patient's chest, the one-way bypass valve 66 remains closedunless atmospheric pressure is exceeded. Thus, the patient is ventilatedonly when the rescuer performing ventilation causes the pressure at theproximal end of the tube 62 to exceed atmospheric pressure. The functionof the one-way bypass valve 66 may be performed by many differentthreshold valve designs which are known in the art.

In another aspect of the invention, an exemplary valving system isprovided for enhancing the duration and extent of negative intrathoracicpressure during the decompression phase of CPR while still providingadequate ventilation to the patient. The valving system is employed toslow the rapid equilibrium of intrathoracic pressure in the chest duringdecompression by impeding or inhibiting the flow of air into thepatient's chest. Lowering of the intrathoracic pressure in this mannerprovides a greater coronary perfusion pressure and hence forces morevenous blood into the thorax. The valving system can be employed in avariety of CPR methods where intrathoracic pressures are intentionallymanipulated to improve cardiopulmonary circulation, including “vest”CPR, CPR incorporating a Heimlich ventilatory system, intraposedabdominal compression-decompression CPR, standard manual CPR, and thelike, and will find its greatest use with ACD-CPR.

Referring to FIGS. 11-15, an exemplary embodiment of a valving system100 is shown schematically. The valving system 100 includes a housing101 having an upstream region 102 and a downstream region 104. Heldbetween the upstream region 102 and downstream region 104 is a diaphragm106. The diaphragm 106 is preferably a flexible or elastomeric membranethat is held over the downstream region 104 to inhibit air from flowingfrom the upstream region 102 to the downstream region 104 when thepressure in the downstream region 104 is less than the pressure in theupstream region 102, except when positive pressure, i.e. greater thanatmospheric, is developed in the upstream region 102 when ventilatingthe patient. The valving system 100 further includes a valve 108 havinga plug 110. As described in greater detail hereinafter, the valve 108 isincluded to provide ventilation to the patient when opened. The valve108 can be manually opened by axial translation or it can beautomatically opened when the pressure in the downstream region 104reaches or exceeds a threshold amount, or both. Included at the upstreamregion 102 is an air intake opening 112 and an air exhaust opening 114.Air is delivered into the housing 101 through the air intake opening112, while air is exhausted from the housing 101 through the air exhaustopening 114. An accordion valve 116, fish mouth valve, or the like isprovided between the air intake opening 112 and the air exhaust opening114. As described in greater detail hereinafter, the accordion valve 116is used to prevent air that is injected into the air intake opening 112from exiting the air exhaust opening 114 when ventilating the patient. Afilter 117 is provided for filtering air injected into the housing 101.Optionally, a filter 119 can be provided in the downstream region 104for preventing excess body fluids and air-borne pathogens from enteringinto the system 100.

Operation of the valving system 100 during compression of a patient'schest is illustrated in FIG. 11. As the patient's chest is compressed,air is forced from the patient's lungs and into the downstream region104. The air forced into the downstream region 104 is directed againstthe diaphragm 106 forcing the diaphragm into an ambient pressure region118. Air in the downstream region 104 is then allowed to escape into theupstream region 102 where it is exhausted through the air exhaustopening 114. Optionally, the diaphragm 106 can be biased so that it willnot be forced into the ambient pressure region 118 until the pressurewithin the downstream region 104 is about 2 cm H₂O or greater, and morepreferably at about 2 cm H₂O to 4 cm H₂O.

Operation of the valving system 100 during decompression (or resting) ofthe patient's chest is illustrated in FIG. 12. As the patient's chest isactively lifted (or allowed to expand on its own), air is drawn from thedownstream region 104 and into the patient's lungs, thereby reducing thepressure in the downstream region 104. The resulting pressuredifferential between the regions 102, 104 holds the diaphragm 106 overthe downstream region 104 to prevent air from the upstream region 102from flowing to the downstream region 104. In this way, air is inhibitedfrom flowing into the patient's lungs during decompression of thepatient's chest, thereby lowering the intrathoracic pressure to increasethe coronary perfusion pressure and to force more venous blood into thethorax.

Various ways of providing ventilation to the patient using the valvingsystem 100 are described in FIGS. 13-15. FIG. 13 illustrates airflowinto the downstream region 104 and to the patient's lungs duringdecompression of the patient's chest after a threshold amount ofnegative intrathoracic pressure has been reached. Ventilation in thismanner is advantageous in that the valving system 100 can be employed toproduce at least a threshold amount of intrathoracic pressure to enhanceblood flow into the heart and lungs. Once such as pressure is reached,some air is allowed to flow to the patient's lungs to ventilate thepatient.

Air is allowed to enter the downstream region 104 when the thresholdamount of intrathoracic pressure is reached by configuring the valve 108to be a threshold valve. The valve 108 can be configured in a variety ofways, with a primary function being that the valve 108 allows air toflow into the downstream region 104 when a threshold amount ofintrathoracic pressure is reached. This is preferably accomplished byconfiguring the plug 110 to be flexible in one direction so that whenthe pressure in the downstream region 104 reaches or exceeds thethreshold amount, the plug 110 is flexed to provide an opening 126between the upstream region 102 and downstream region 104. When the plug110 is flexed, air flows from the lower pressure upstream region 102into the downstream region 104 and to the patient's lungs. The plug 110therefore acts as a one-way valve allowing air to flow from the upstreamregion 102 into the downstream region 104 when the threshold amount isreached, but does not allow airflow from the downstream region 104 tothe upstream region 102. Preferably, the plug 110 will flex to open whenthe pressure within the downstream region 104 is in the range from about0 mm H₂O to 50 cm H₂O, more preferably at about 10 cm H₂O to 40 cm H₂O,and more preferably at 15 cm H₂O to about 20 cm H₂O. Alternatively, thevalve 108 can be placed in the downstream region 104 so that air flowsinto the downstream region 104 directly from the atmosphere when thevalve 108 is open. Although shown as a flexible plug, it will beappreciated that other types of valve arrangements may be used. Forexample, plug 110 could be replaced with a spring biased valve thatcloses opening 126 until the negative intrathoracic pressure overcomesthe force of the spring to open the valve in a manner similar to thatdescribed in connection with FIG. 16A.

Ventilating the patient by injecting air into the upstream region 102 isillustrated in FIG. 14. As air is injected through the intake opening112, it passes into the accordion valve 116 and forces the valve 116against a wall 120 and covers a hole 122 in the wall 120 to preventairflow through the exhaust opening 114. When the accordion valve 116 isclosed, air flows through a wall 124 of the valve 116 and into theupstream region 102. Alternatively, a fish mouth valve can be used inplace of the accordion valve 116. Upon injection of the air into theupstream region 102, the pressure within the upstream region 102 becomesgreater than the pressure in the ambient pressure region 118 and causesthe diaphragm 106 to be drawn into the ambient pressure region 118. Anopening between the upstream region 102 and the downstream region 104 iscreated allowing air to flow into the downstream region 104 and into thepatient's lungs. Preferably, the patient will be manually ventilated byinjecting air into the intake opening 112 one time every fivecompressions of the chest, and more preferably about two times every 15compressions of the chest using two rescuers. Similarly, ventilating thepatient can occur through the same port where the spring-biased valve islocated, such as through valve 160 of FIG. 16A.

Configuration of the valving system 100 upon return of spontaneouscirculation is illustrated in FIG. 15. When the patient's circulation isrestored, the valve 108 is manually opened by translating the valve 108to remove the plug 110 from aperture 126. The upstream region 102 anddownstream region 104 are then placed in communication to allow air tobe freely exchanged between each of the regions 102, 104. Although shownextending through the upstream region 102, the valve 108 canalternatively be placed anywhere along the downstream region 104.

The valve 108 can be configured as a pressure-responsive valve (see FIG.13), as a manually operable valve (see FIG. 15), or both. Further, thevalving system 100 can alternatively be provided with two or more valvesthat are similar to the valve 108. For example, one valve could benon-translatably held in the housing 101 and provided with apressure-responsive plug 110, with the other valve being translatablymounted. In this manner, the valve with the flexible plug functions as apressure-responsive valve and opens when the threshold pressure isreached, while the translatable valve functions to place the regions102, 104 in communication upon manual operation after spontaneouscirculation is achieved.

Referring to FIGS. 16A and 16B, an exemplary embodiment of a valvingsystem 130 will be described. The valving system 130 is constructed of ahousing 132 having an intake opening 134, an exhaust opening 136, and adelivery opening 138. Included in the exhaust opening 136 is a one-wayvalve 140 which allows air to flow from the housing 132 and out theexhaust opening 136. An accordion valve 140 is provided between theintake opening 134 and an exhaust opening 136 to prevent air injectedinto the intake opening 134 from exiting through the exhaust opening136. Preferably, the intake opening 134 is configured to be attachableto a respiratory device, such as a respiratory bag (including an AMBUbag), a ventilator, a mouthpiece or port for mouth-to-mouth breathingthrough the system 130, or the like. The delivery opening 138 ispreferably configured for connection to an endotracheal tube or otherairway tube, a sealed facial mask, a laryngeal mask, or the like.

Within the housing 132 is an upstream region 142, a downstream region144, and an ambient pressure region 146. Separating the upstream region142 from the downstream region 144 is a diaphragm 148. The diaphragm 148is preferably constructed of an elastomeric material. The housing 132 ispreferably cylindrical in geometry at the downstream region 144, withthe diaphragm 148 resting on the cylinder during ambient conditions.During decompression of the patient's chest, the reduction in pressurein the downstream region 144 draws the diaphragm 148 against the end ofthe cylinder to prevent exchange of air between the upstream region 142and downstream region 144. During compression of the patient's chest,air is forced into the downstream region 144 to force the diaphragm 148into the ambient pressure region 146 so that the air exhausted from thepatient's chest can be exhausted through the exhaust opening 136.

As shown best in FIG. 16B, the valving system 130 is further providedwith a fenestrated mount 150. In one aspect, the fenestrated mount 150serves as a mount for holding the diaphragm 148 over the downstreamregion 144. The fenestrated mount 150 further provides the ambientpressure region 146. Fenestrations 152 are provided in the mount 150 toallow air to be exchanged through the mount 150. Included on the mount150 is a deflector 154 for deflecting air around the fenestrated mount150. Various other deflectors 156 are provided in the housing 132 fordirecting airflows between the regions 142 and 144. A filter 158 isprovided in the housing 132 to filter air injected into the housing 132.Optionally, a filter 159 can be provided to prevent excess body fluidsfrom entering into the system 130.

The valving system 130 further includes a threshold valve 160 at thedownstream region 144. When the pressure within the downstream region144 is less than the threshold amount, the threshold valve 160 is openedto allow air to flow into the downstream region 144. The threshold valve160 includes a spring 162 which is configured to extend when thethreshold amount is reached. Alternatively, the threshold valve 160 canbe configured similar to the valve 110. Other configurations which allowthe for air to enter the downstream region 144 when the desiredintrathoracic pressure is reached or exceeded can also be provided. Forexample, in a further alternative, the diaphragm 148 can be constructedto function as a threshold valve to allow air to flow into the patient'slungs when a threshold amount of intrathoracic pressure is reached. Thediaphragm 148 can be fashioned as a threshold valve by constructing thediaphragm 148 of an elastomeric material and by providing at least onehole near the periphery. When the diaphragm rests on the cylinderforming the downstream region 144, the hole is positioned beyond theperiphery of the cylinder and in the upstream region 142. As a vacuum iscreated in the downstream region 144, the diaphragm is drawn into thedownstream region 144 until the hole is stretched over the cylinder andoverlaps with both the upstream region 142 and the downstream region144. In this way, a fluid path is provided between the regions 142 and144 when the threshold pressure is reached in the downstream region 144.Another alternative of a threshold valve 111 is illustrated in FIG. 16C.The valve 111 is pivot mounted within the downstream region 144 and isbiased closed by a spring 113. When the threshold pressure within thedownstream region 144 is reached, the spring 113 is compressed and airis drawn into the downstream region 144.

Referring back to FIG. 16A, the threshold valve 160 can optionally beprovided within the housing 132 at the upstream region 142. Thethreshold valve 160 can further optionally be provided with an on/offswitch for opening the valve 160 when spontaneous circulation isachieved. In this manner, a rescuer can open the valve 160 to allow forfree exchange of air to the patient's lungs when needed. In onealternative as shown in FIG. 16C, the mount 150 can be slidably mountedwithin the housing 132 so that the mount 150 can be vertically raised tolift the diaphragm 148 from the downstream region 144 upon successfulresuscitation of the patient, thereby providing a free flow of air tothe patient. The mount 150 can be slidably mounted within the housing132 by attaching the mount 150 to an extension member 133 that isslidable within the housing 132. The member 133 preferably includes theintake and exhaust openings 134 and 136. In this way, an easy graspingsurface is provided when translating the member 133 to open or close thediaphragm 148. If the diaphragm 148 were also fashioned as a thresholdvalve as previously described, the need for the valves 108 or 111 couldbe eliminated.

The housing 132 can conveniently be constructed in several parts whichare connected together at various connection points. In this manner, thehousing can be taken apart for connection to other devices, for repair,for cleaning, and the like. For example, one connection point can beconveniently provided near the filter 158 for removably connecting theportion of the housing having the intake opening 134, the valve 140, andthe exhaust opening 136. Alternatively, a connection point can beprovided near the mount 150 to provide easy access to the mount 150 forcleaning.

The valving system 130 can conveniently be incorporated with a varietyof devices useful in CPR procedures. For example, the valving system 130can be incorporated within a respiratory bag, such as an AMBU bag.Alternatively, the valving system 130 can be included as part of arespiratory circuit having both a respiratory bag and an endotrachealtube or other airway tube, with the valving system 130 positionedbetween the bag and the tube. In further alternative, the valving system130 can be added to an endotracheal tube alone. Alternatively, thevalving system can be incorporated into a mask, an oralpharyngealairway, a laryngeal mask or other ventilatory devices.

In some cases, patient ventilation may be provided through thresholdvalve 160 as shown in FIG. 16D. In such a case, intake opening and valve140 are optional since all ventilation may occur through threshold valve160. Of course, ventilation could be provided through both avenues.Further, although shown in the context of valving system 130, it will beappreciated that the other embodiments described herein may be modifiedto include a pressure source that is coupled to the threshold valve.

As shown in FIG. 16D, a tank 300 of pressurized gas, such as 02 iscoupled to housing 132 by a length of tubing 302. In this way, apressurized gas may be supplied to the back side of threshold valve 160.A regulator 304 is coupled to tank 300 to regulate the pressure suppliedto threshold valve 160 so that it is less than the pressure required toopen valve 160. For example, if respiratory gases are to be supplied tothe patient when the negative intrathoracic pressure exceeds −14 cm H20,then the actuating valve pressure may be set at −14 cm H20, and thepressure of the gas from tank 300 may be set less than 14 cm H₂O. Inthis way, valve 160 will not prematurely open. In some cases, regulator304 may also be used to regulate the flow rate of the gas through valve160.

By coupling tank 300 to valve 160, respiratory gases are pulled intodownstream region 144 when valve 160 opens due to the decrease innegative intrathoracic pressure as previously described. In this way,more respiratory gases are supplied to the patient each time thepatient's chest is decompressed. This approach allows for negativepressure ventilation, unlike positive pressure ventilation which impedesvenous return to the chest with each active rescuer ventilation. Thenegative pressure ventilation with this approach allows for adequateoxygenation and maximum venous blood return during CPR. Tank 300 mayalso function to provide oxygen once the trigger pressure has beenachieved.

Referring to FIG. 17, an alternative valving system 164 will bedescribed. The valving system 164 is shown schematically and operatesessentially identical to the valving system 100, the difference beingthat the valving system 164 includes a ball or spherical member 166 asthe diaphragm. During decompression of the patient's chest, the pressurein a downstream region 168 is less than the pressure in an upstreamregion 170 which draws the ball 166 over the downstream region 168. Thevalving system 164 can optionally be provided with a spring 172 or otherbiasing mechanism to hold the ball 166 over the downstream region 168during compression of the patient's chest until a threshold pressure isreached or exceeded in the downstream region 168 as previouslydescribed.

Referring now to FIG. 18, another exemplary device 200 which is usefulwhen performing cardiopulmonary resuscitation will be described. Asdescribed in greater detail hereinafter, one important feature of device200 is that it may be interfaced to the patient's airway to periodicallysupply air to the patient's lungs when performing cardiopulmonaryresuscitation. In this way, the patient may be ventilated with air (orother desired gases, such as O₂) rather than with respiratory gases fromthe rescuer's lungs as is typically the case when performingmouth-to-mouth resuscitation.

Device 200 comprises a facial mask 202 and a housing 204 that isoperably attached to facial mask 202 at an interface 206. Housing 204includes an upper region 208 and a lower region 210. Lower region 210includes a pressure responsive valving system 212 which operates in amanner similar to the embodiments previously described herein to preventthe flow of gases into the patient's lungs until a threshold negativeintrathoracic pressure is exceeded. At this point, pressure responsivevalving system 212 allows gases to flow into the patient's lungs in amanner similar to that previously described herein. Lower region 210further includes a fish mouth valve 214 and one-way outflow valves 216.Valves 214 and 216 operate together to allow gases exhausted from thepatient's lungs to exit device 200 as indicated by arrow 218. Inparticular, when gases are forced out of the patient's lungs, fish mouthvalve 214 will be closed and the exhausted gases will escape from device200 through valves 216.

Upper region 208 includes a mouth piece 219 to allow a rescuer to blowinto device 200 when attempting to ventilate a patient (similar toconventional CPR). Upper region 208 defines an air chamber 220 forholding room air and has a volume of about 200 ml to about 800 ml.Chamber 200 may also be connected to an oxygen source. Disposed withinupper region 208 is a diaphragm 222 and a spring 224. With thisconfiguration, when a rescuer blows air into mouth piece 219, spring 224will compress as diaphragm 222 moves downward. In turn, air or oxygenheld within air chamber 220 will be compressed and hence forced throughvalving system 212 and into facial mask 202. In this way, air (ratherthan respiratory gases) from the rescuer will be supplied to the patientwhen the rescuer performs mouth-to-mouth resuscitation by blowing intomouth piece 219.

Upper region 208 further includes a one-way inflow valve 226 whichallows air chamber 220 to be replenished with room air followingventilation. In particular, as spring 224 expands valve 226 will open toallow room air to fill chamber 230 due to the negative pressure createdin chamber 230 by spring 224. Inflow valve 226 will also open when thethreshold negative intrathoracic pressure is exceeded causing pressureresponsive valving system 212 to open. In this way, inflow valve 226also serves as a venting mechanism to vent air into housing 204 when thenegative intrathoracic pressure limit is exceeded.

Hence, device 200 allows a rescuer to ventilate a patient with room airsimply by blowing into mouth piece 219. Of course, it will appreciatedthat other desirable gases may be placed within air chamber 220 so thatsuch gases may be supplied to the patient when the rescuer blows intomouth piece 219. For example, a volume of O₂ may be placed withinchamber 220.

As previously described, one aspect of the invention is the ability toprevent respiratory gasses from entering the lungs until a certainnegative intrathoracic pressure is met or exceeded. One aspect of theinvention is the ability to vary the pressure at which respiratorygasses are permitted to flow to the lungs. In some cases, this may beaccomplished by varying the actuating or cracking pressure of thepressure-responsive inflow valve. However, other mechanisms may beprovided to vary the pressure at which respiratory gasses are permittedto flow to the lungs without modifying the cracking pressure of thepressure-responsive inflow valve. Hence, mechanisms for varying thepressure at which respiratory gasses are permitted to flow to the lungsmay be incorporated in the pressure-responsive inflow valve, anothervalve in the valving system, or may be a separate part of the overallvalving system.

Such a system may be configured so that the actuating pressure may varybetween about 0 cm H₂O to about −30 cm H₂O. Further, such a valvingsystem may be used alone with a spontaneous breathing patient or with apatient receiving standard manual closed-chest CPR. Such a valvingsystem may also be used in conjunction with other resuscitationtechniques and/or devices, including, for example, ACD CPR, Vest CPR, orthe like. In some cases, such a valving system may be used in connectionwith a diaphragmatic stimulator for purposes of resuscitation fromcardiac arrest as well as for increasing blood pressure by advancingvenous return. Exemplary systems and techniques for diaphragmaticstimulation for purposes of resuscitation are described in U.S. patentapplication Ser. No. 09/095,916, filed Jun. 11, 1998; Ser. No.09/197,286, filed Nov. 20, 1998; Ser. No. 09/315,396, filed May 20,1999; and Ser. No. 09/533,880, filed Mar. 22, 2000, incorporated hereinby reference. As a further example, such a valving system may be used toimprove central blood return to the heart in patients in cardiac arrest,patients with low blood pressure and patients in right heart failure andin shock.

A variety of mechanisms may be used to vary the degree at whichrespiratory gasses are permitted to flow to the lungs. For example, sucha mechanism may be mechanical or electronic or may include variouscombinations of mechanical and electronic components, and may beregulated within a larger system by, for example, electroniccommunication between the device used for resuscitation and thepressure-responsive inflow valve. Such a mechanism may also beadjustable based upon the in-line measurement of gasses, such as themeasurement of end-tidal CO₂, the average minute ventilations, peaknegative inspiratory pressures, and the like.

Referring to FIG. 19, one embodiment of a valving system 400 having anadjustable pressure-responsive inflow valve 402 will be described.Valving system 400 is shown schematically and may be constructed similarto any of the embodiments described herein. As such, when valving system400 is interfaced with a patient's airway, the patient may freely exhalethrough valving system 400. When attempting to inhale, or during adecompression step of CPR, respiratory gasses are prevented fromentering the lungs until a threshold actuating pressure is reached. Atsuch time, respiratory gasses are permitted to flow to the lungs throughinflow valve 402 in a manner similar to that previously described withother embodiments.

Inflow valve 402 includes a tension adjust knob 404 that may be turnedby the rescuer to adjust the threshold actuating pressure of inflowvalve 402 and will be described in greater detail with reference toFIGS. 20-22. As best shown in FIG. 20, inflow valve 402 comprises anouter housing 406 having a set of tracking channels 408 (see FIG. 22).Outer housing 406 is configured to hold an O-ring housing 410 having atop segment 412 and a bottom segment 414. Disposed between top segment412 and bottom segment 414 is an O-ring 416. Top segment 412 furtherincludes a set of tracking rails 418 that slide within tracking channels408. A tension spring 420 sits between tension adjust knob 404 and topsegment 412 and biases O-ring 416 against outer housing 406. When O-ring416 is biased against outer housing 406 the valve is in the closedposition where respiratory gasses are prevented from passing throughventilation ports 422 and to the patient's lungs. When the negativeintrathoracic pressure meets or exceeds the threshold actuating pressureof inflow valve 402, the tension in spring 420 is overcome, causingO-ring 416 to separate from outer housing 406. At this point,respiratory gasses are free to rush through ventilation ports 422 and tothe patient's lungs.

To vary the actuating pressure of inflow valve 402, knob 404 is turnedto advance or retract a threaded nut 424 along a threaded bolt 426 thatin turn is coupled to top segment 412. In so doing, the tension ofspring 420 is varied to vary the actuating pressure of inflow valve 402.Hence, knob 404 provides a convenient way for a rescuer to adjust theactuating pressure simply by turning knob 404. Although not shown, apressure gauge may be disposed within valving system 400 and a displaymay be provided to display the negative intrathoracic pressure. In thisway, the rescuer may readily visualize the pressures generated withinvalving system 400 and may adjust knob 404 to vary the pressure at whichrespiratory gasses are permitted to flow to the lungs.

Another feature of the invention is the use of a safety mechanism topermit respiratory gasses to freely flow to the patient through thevalving system until the rescuer places the valving system in anoperative mode. Once in the operative mode, the valving system willremain in that mode indefinitely or for a finite period of time, atwhich the safety mechanism would revert back to its initial state whererespiratory gasses may freely flow to the lungs. In some embodiments,this may be accomplished by having the safety mechanism maintain thepressure responsive inflow valve in the open position (without anyimpedance to inspiratory air flow) until actuated by the rescuer.Actuation may be accomplished in a variety of ways, such as by injectedrespiratory gasses into the valving system (such as when ventilating thepatient), by operating a button or switch on the valving system, or thelike.

One advantage of such a safety mechanism is that it ensures that thepatient can freely breathe through the valving system (assuming thepatient is spontaneously breathing or begins to spontaneous breathe)without any resistance from the pressure-responsive inflow valve. Oncethe rescuer is ready to begin a procedure, such as performing CPR, thevalving system is placed in the operative mode where respiratory gasflow to the lungs is prevented through the pressure-responsive inflowvalve until the threshold negative intrathoracic pressure is met orexceeded. As with other embodiments described herein, respiratory gassesmay also be injected into the patient's lungs through the valvingsystem, thereby bypassing the pressure-responsive inflow valve.

The safety mechanism may operate as a purely mechanical device, a purelyelectronic device, or may include various combinations of mechanical andelectronic components. One way for placing the valving system in theoperative mode is by utilizing a sensor to detect when respiratorygasses are injected into the valving system through the ventilator port.The signal from the sensor may then be used to close a ventilationpassage within the valving system. In some cases, the ventilationpassage may extend through the pressure-responsive inflow valve. Toclose this passage, the inflow valve is simply closed. In someembodiments, if rescuer ventilation is not provided within a certaintime, the safety mechanism may be used to take the valving system out ofits operative mode so that respiratory gasses may freely flow to thepatient's lungs.

Referring now to FIGS. 23 and 24, one embodiment of a valving system 430with such a safety feature will be described. This configuration may beused in series with any of the previously described valving systems sothat it will have a means of impeding airflow to the patient's lungs.Hence, it will be appreciated that valving system 430 may be constructedto have, or used in combination with, components similar to the othervalving systems described herein and will not be illustrated to simplifydiscussion. Valving system 430 includes a housing 432 that may besimilar to the housings of the other valving systems described hereinexcept that housing 432 includes a safety ventilation port 434 thatpermits respiratory gasses to flow into and through housing 432 so thatrespiratory gasses may flow to the patient's lungs as shown by thedashed line in FIG. 23. Hence, as shown in FIG. 23, valving system 430is in a passive mode where the patient may freely breathe throughhousing 432.

Valving system 430 further includes a safety mechanism 436 that isoperative to maintain ventilation port 434 open until actuated by arescuer. When actuated, safety mechanism 436 closes ventilation port 434to place valving system 430 in the operative mode where respiratorygasses are prevented from reaching the lungs through apressure-responsive inflow valve until a threshold negativeintrathoracic pressure is met or exceeded in a manner similar to thatdescribed in other embodiments.

Safety mechanism 436 comprises an electronic air flow sensor 438 that iselectrically connected to control circuitry 440. In turn, controlcircuitry 440 is electrically connected to a micro-solenoid 442 having avalve stop 444. A battery 445 is used to supply power to the electricalcomponents. When a rescuer is ready to place valving system 430 in theoperative mode, the rescuer injects respiratory gasses into housing 432(such as by blowing air or injecting a pressurized gas into aventilation port, not shown). As the respiratory gasses flow to thepatient's lungs through housing 432, sensor 438 is moved to trigger aswitch and to send an electrical signal to control circuitry 440.Control circuitry 440 then sends a signal to solenoid 442 to move stop444 and thereby close the valve, thus preventing airflow to the patientthrough safety ventilation port 434. Such a state is illustrated in FIG.24 where valving system 430 is in the operative mode. At this point, aspontaneously breathing patient will need to breathe through apressure-responsive inflow valve. For a non-breathing patient,respiratory gasses will be prevented from reaching the lungs during theperformance of CPR until a threshold negative intrathoracic pressure isovercome, at which point respiratory gasses may flow through the inflowvalve and to the patient's lungs in a manner similar to that describedwith other embodiments. If, after a certain time, sensor 438 is notactuated by the rescuer, control circuitry 440 may be configured tooperate solenoid 442 to take valving system 430 out of the operativemode where respiratory gasses may flow through safety ventilation port434.

In some embodiments, the valving systems of the invention mayincorporation a safety mechanism having essentially all mechanicalelements. One such embodiment of a valving system 480 is illustrated inFIGS. 25 through 33 and 36 through 40. Valving system 480 comprises ahousing 482 that houses various components that may be similar to theother embodiments described herein. As such, housing 482 includes aventilation port 484 and an exit opening 486. Valving system 480 furtherincludes a pressure-responsive inflow valve 488 that preventsrespiratory gasses from flowing to the patient's lungs until a certainnegative intrathoracic pressure level has been met or exceeded in amanner similar to that described with other embodiments. Valving system480 further includes a safety mechanism 490 to permit respiratory gassesto freely flow to the patient's lungs until operated to place valvingsystem 480 in an operative mode where pressure-responsive inflow valve488 controls when respiratory gasses are permitted to flow to the lungs.As described in greater detail hereinafter, safety mechanism 490 alsoincludes an inflow valve 492. In some embodiments, inflow valve 492 maybe configured as a pressure-responsive inflow valve and therebyeliminate the need for inflow valve 488.

Safety mechanism 490 further comprises a flow sensor 494 that is in theform of a flap. Flow sensor 494 pivots about a pivot point 496 to move acam mechanism 498, thereby rotating a wheel 500. In FIGS. 25 and 30,valving system 480 is in the inactive state where flow sensor 494 hasnot yet been activated. When respiratory gasses are directed throughhousing 482, flow sensor 494 pivots about pivot point 496 as previouslydescribed to rotate wheel 500 as illustrated in FIGS. 27, 28 and 30.

As best shown in FIG. 29, wheel 500 is connected to a gear system 502having a recoil spring 504 and a valve cam 506. Recoil spring 504 isemployed to bias cam 506 in the position illustrated in FIGS. 25 and 30where valve 492 is in the open position. When gasses flow throughhousing 482, flow sensor 494 is moved to cause wheel 500 to rotate andthereby operate gear system 502. In so doing, cam 506 is rotated to theposition shown in FIGS. 27 and 31 where valve 492 moves to the closedposition. Gear system 502 and recoil spring 504 operate to open valve492 after a certain period of time has elapsed, such as about 10 to 20seconds.

As best shown in FIGS. 30 and 31, valve 492 comprises a valve housing508 in which is held a valve shaft 510 that holds an O-ring 512. Atension spring 514 is positioned between housing 508 and a projection516 on shaft 510 to bias the valve 492 in the closed position asillustrated in FIG. 31. When a rescuer injects respiratory gasses intothe housing of the valving system, cam 506 moves to the position shownin FIG. 30 where it engages shaft 510 and disengages O-ring 512 fromhousing 508 to place valve 492 in the open position. In the openposition, respiratory gasses are free to flow through valve 492 and intohousing 482 where they may flow to the patient's lungs through exitopening 486.

The invention further provides systems having safety features that allowfor the patient to inhale to a given degree to release the mechanismthat is used to impede or prevent respiratory gases from flowing to thelungs, thereby allowing for resistance free inspiration until a timerresets the systems or until the rescuer resets the system. Oneembodiment of a safety valve 600 that may be used with such systems isillustrated in FIGS. 32 and 33. Safety valve 600 may be used as areplacement for any of the pressure responsive valves described herein,such as, for example, valves 108, 160 and 111. Valve 600 comprises ahousing 602 which is covered by a slit membrane 604. A valve member 606is biased by a spring 608 into a closed position as shown in FIG. 32. Inthe closed position, a wedge 610, that may conveniently be colored foreasy identification, extends above the slit in membrane 604. As such,wedge 610 serves as a visual indicator to the rescuer that valve 600 isin the closed position. When interfaced with a patient and in the closedposition, respiratory gases may be prevented from flowing to the lungsuntil the negative intrathoracic pressure meets or exceeds a thresholdvalue in a manner similar to that described with other embodiments. Atsuch time, a seal 612 on valve member 606 moves away from a stop 614 onhousing 602 to permit respiratory gases to flow to the lungs. Spring 608then forces valve member 606 back to the closed position.

If the patient gasps and begins to breath, the amount of negativepressure created by the patient compresses spring 608 far enough so thatwedge 610 is pulled through the slit in membrane 604 as shown in FIG.33. Wedge 610 then holds valve 600 in the open position where gases mayfreely flow to the lungs. The rescuer may easily determine valve 600 isin the open position by noticing that wedge 610 is no longer visible.The rescuer may reset valve 600 at any time by simply pulling on a pulltab 616 to pull wedge 610 back through membrane 604.

Another embodiment of a safety valve 620 that may be used in the systemsdescribed herein is illustrated in FIGS. 34 and 35. Valve 620 comprisesa housing 622 having a stop 624. A micro-solenoid 626 is disposed withinhousing an includes an arm 628 having a pole magnet 629 and a visualindicator 630 at an opposite end. Spaced apart from pole magnet 629 isanother pole magnet 632 of opposite polarity that is coupled to a valvemember 634 having a seal 636. Coupled to housing 622 is a normally opencontact strip switch 638, and valve member 634 includes a conductivestrip 640. A spring 642 is disposed between strip 640 and stop 624.

FIG. 34 illustrates valve 620 in the closed or active position. DuringCPR, seal 636 will separate from stop 624 to permit respiratory gases toflow to the lungs when the negative intrathoracic pressure exceeds athreshold value. Valve 620 then returns back to the closed position. Ifthe patient gasps, valve member 634 moves to the position shown in FIG.35 where conductive strip 640 contacts switch 638. (During normal CPR,valve member 634 is not moved far enough for this contact to occur).This closes the open circuit and activates solenoid 626 to extend arm628 and trigger a timing circuit within a control circuitry and batterycompartment 644. Magnets 629 and 632 have opposite poles causing valveto remain in the open and inactive position as shown in FIG. 35 as longas solenoid 626 is actuated. In this way, the patient may continue tofreely breath through valve 620. Although shown with opposing polemagnets, it will be appreciated that magnets may be substituted with asolenoid arm that may act as a plunger to make physical contact withvalve member 634, and thus hold the valve open and inactive. The rescuermay note that valve 620 is in the open position by noting that indicator630 has been retracted and is no longer visible.

Valve 620 may include an auto/manual switch 646 that may be set inautomatic mode. In this mode, the timing circuit automaticallydeactivates solenoid 626 and returns valve 620 back to the closed andactive position shown in FIG. 34 after a preset timing interval hasexpired. If switch 646 is set to manual, solenoid 626 remains active andvalve 620 remains open and inactive as shown in FIG. 35 whererespiratory gases may freely flow to the lungs. Valve 620 remains openuntil the rescuer manually resets solenoid 626 by pressuring a manualreset switch 648. The rescuer may note that valve 620 is closed andactive by observing indicator 630 that is now extended.

FIGS. 36 and 37 illustrate a further embodiment of a safety valve 650that may be used with the systems described herein. Valve 650 comprisesa housing 652 having a stop 654. Disposed within housing 652 is a valvemember 656 having a seal 658 that contacts stop 654 to prevent gasesfrom flowing through valve 650 when in the closed or active positionshown in FIG. 36. In the closed position, a spring 660 biases seal 658against stop 654 until the negative intrathoracic pressure exceeds athreshold value and seal 658 moves away from stop 654 to permitrespiratory gases to flow to the lungs. Once the negative intrathoracicpressure falls below the threshold value, valve 650 moves back to theclosed position.

When the patient gasps, the force created is great enough to move valvemember 656 such that a pair of spring loaded pins 662 lodge withingrooves 664 of a locking pin receptacle 666 on valve member 656 as shownin FIG. 37. In this way, valve 650 is locked into an open or inactiveposition that is created by the patient's gasp. As pins 662 move intogrooves 664, the ends of pins 662 move into housing 652 to indicate tothe rescuer that the valve is inactive. Conveniently, the ends of pins662 may be colored to make them more visible to the rescuer. Toreactivate valve 650, the rescuer may pull upward on a pull tab 668 onvalve member 656. This releases pins 662 from grooves 664 and permit thevalve to spring back to the closed position of FIG. 36.

Referring now to FIGS. 38-40, a modified version valve 650 is shownincorporated into a valve system 670 that may be coupled to a patient'sairway in a manner similar to the other valve system embodimentsdescribed herein to regulate the airflow to the patient's lungs during aCPR procedure. For convenience of discussion, identical elements ofvalve 650 will use the same reference numerals in describing FIGS.38-40. The use of valve 650 allows the patient to gasp and breathe freeof airway resistance after the initial gasp has occurred. Alternatively,valve 650 may be initially set in the inactive position and placed inthe active state upon the initial ventilation through valve system 670,or upon subsequent ventilations if the patient gasps and locks valve 650open and inactive.

Valve 650 is incorporated into a system housing 672 having an inlet end674 and an outlet end 676. Conveniently, patient ventilation may occurthrough inlet end 674 using a ventilatory source similar to otherembodiments. Outlet end 676 may be coupled to an interface that permitssystem 670 to be interfaced with the patient's airway. Disposed withinhousing 672 is a one way membrane valve 678 that is spaced apart fromport 680. In FIG. 38, system 670 is in the resting state where no gaspor ventilation has occurred. When performing CPR, the chest iscompressed and air forced from the patient is permitted to flow throughport 680 and through valve 678. During decompression of the patient'schest, valve membrane 678 moves against port 680 to close the valve asthe negative intrathoracic pressure is increased. If a thresholdpressure is overcome, valve 650 opens to permit respiratory gases toflow through opening 676 after passing through valve 650. Valve 650 thenmoves back to the closed position and the cycle is repeated.

If valve system 670 is coupled to a patient's airway and the patientgasps or begins spontaneously breathing, valve system 670 automaticallyadjusts to the configuration shown in FIG. 39 so that the patient maybreathe through a resistance fee airway path so that respiratory gasexchange may occur. When the patient gasps or begins to breathe, valve678 closes and the negative pressure causes valve 650 to open and lockin place in a manner similar to that previously described in connectionwith FIG. 37. In this way, valve 650 remains open and inactive untilreset by the rescuer by pulling on pull tab 668.

Another way to place valve 650 back into the closed or active positionis by ventilating the patient through inlet 674 as shown in FIG. 40.When injecting a respiratory gas into inlet 674, the injected gases flowthrough valve 678 and through port 680 where the exit through outlet 676and to the patient. In so doing, the flow of gases moves a ventilationflap 682 that in turn moves an arm 684 that is coupled to a wedge 686.Movement of wedge 686 causes lateral movement of an arm 688 that isconnected to a reset wedge 690. Wedge 690 rests on top of an upwardmovement ramp 692. As arm 688 is laterally moved, wedge 690 moves upramp 692 and contacts pull tab 668. In so doing, valve member 656 ispulled up until pins 662 are pulled from grooves 664 and valve 650 movesback to the closed and active position by force of spring 660. A resetspring 694 then resets ventilation flap 682 back to its home positionand wedge 690 slides back down ramp 692 so that valve 650 may be resetback to the closed position if subsequently needed. Valve 650 remains inthe closed and active position until another gasp or spontaneousbreathing occurs.

FIG. 41 schematically illustrates another embodiment of a valving system700 that is configured to display the pressure within the patient'schest during CPR. Valving system 700 may be configured to be similar toany of the valving systems described herein. Hence, for convenience ofdiscussion, valving system 700 will only be briefly described. Valvingsystem 700 comprises a housing 702 having an inlet 704 and an outlet706. A pressure responsive valve 708 is used to control the inflow ofgases into housing 702 during decompression of the patient's chest in amanner similar to that described with other embodiments. A pressuregauge 710 is provided to measure and display the pressure within housing702 which corresponds to the pressure within the patient's chest. Inthis way, pressure gauge 710 may be used to provide immediate feedbackto the rescuer and may be used as a guide to determine if chestcompressions and/or decompressions are being appropriately performed.

A pressure sensing port 712 is connected to a tube 714 that is connectedto a pressure sensing control unit 716. In this manner, a change inpressure may be detected during either chest compressions ordecompressions and act as a counting circuit to trigger ventilationcontrol circuitry 718 to automatically ventilate the patient using aventilator 720 after a certain number have been detected.

Alternatively, a digital control unit may be used that displays thepressure within the chest as well as the number of compressions betweenventilations. With such a configuration, pressure sensing port 712transmits pneumatically the pressure information. As such, a pressuregauge on housing 702 would not be required.

The valving systems of the invention may also be used to treat shock.Shock may conveniently be defined as a critically low blood pressurethat, when untreated, may lead to death or disability. Types of shockthat may be treated using techniques of the invention include, but arenot limited to, low blood pressure secondary to blood loss, heat stroke,vasovagal syncope (the common faint), drowning, drug overdose, heartattack, right heart failure, return to earth after space flight, sepsis,pericardial effusion, tamponade, and the like. Further, the valvesystems of the invention may be used to alter the carotidcardiopulmonary reflex sensitivity that controls blood pressure (bydecreasing intra thoracic pressures with inspiration).

The valve system that are employed to treat shock are configured tocompletely prevent or provide resistance to the inflow of respiratorygases into the patient while the patient is breathing. For valve systemsthat completely prevent the flow of respiratory gases, such valves maybe configured as pressure responsive valves that open after a thresholdnegative intra thoracic pressure has been reached. Valve systems thatsimply provide resistance to the inflow of respiratory gases may also bevariable so that once a desired negative intra thoracic pressure isreached, the resistance to flow may be lessened. Further, the valves ofthe invention may be configured to be variable, either manually orautomatically. The extent to which the resistance to flow is varied maybe based on physiological parameters measured by one or more sensorsthat are associated with the person being treated. As such, theresistance to flow may be varied so that the person's physiologicalparameters are brought within an acceptable range. Examples ofphysiological parameters that may be measured include, but are notlimited to, negative intra thoracic pressure, respiratory rate, endtidal CO₂, positive end expiratory pressure, blood pressure, oxygensaturation, tissue CO₂ content, and the like. If an automated system isused, such sensors may be coupled to a controller which is employed tocontrol one or more mechanisms that vary the resistance or actuatingpressure of the inflow valve.

Referring now to FIGS. 42 and 43, one embodiment of a system 800 thatmay be used to treat a person in shock will be described. System 800comprises a housing 802 that is coupled to a facial mask 804. Housing802 includes an inspiratory fenestrated port 806 where inspired gasesare permitted to enter housing 802. Disposed below port 806 is a slottedairway resistance mechanism 808 that may be used to completely preventor provide resistance to the respiratory gases flowing into housing 802through port 806. Resistance mechanism 808 is also illustrated in FIGS.46A and 46B and may be constructed of a slotted member 810 and a slottedplate 812. Slotted member 810 is movable relative to plate 812 topartially or fully cover the slots in plate 812 as illustrated in FIG.46B. In this way, the resistance to the flow of inspired gases may beincreased simply by moving slotted plate 812 relative to slotted member810. As best shown in FIG. 42, a motor 814 that moves a shaft 816 may beemployed to translate slotted member 810 over slotted plate 812 to varythe resistance to flow. Optionally, a filter 818 may be disposed belowresistance mechanism 808.

System 800 further includes a one-way valve 820 that prevents expiredgases from flowing back up through resistance mechanism 808. Disposedupstream of one-way valve 820 is an oxygen port 822 to permit oxygen tobe supplied to the person during inspiration. System 800 furtherincludes another one-way valve 824 that opens when the person expires topermit expired gases from exiting housing 802 through an expiratory port826.

System 800 may also include one or more sensors 828 that measure variousphysiological parameters, such as flow rate, internal pressures withinthe patient, end tidal CO₂, and the like. These sensors may be coupledto a circuit board or controller 830 that may be programmed to varyoperation of motor 814 based on the sensed parameters. In this way, themeasured parameters may be kept within a desired range simply bycontrolling the resistance provided by resistance mechanism 808 in anautomated manner. Although not shown, it will be appreciated that othersensors may also be coupled to circuit board 830 and may not necessarilybe incorporated into housing 802 or mask 804. System 800 may alsoinclude a battery 832 to provide power to the various electricalcomponents of system 800. A control button 834 may also be employed toactuate system 800.

Optionally, to ensure that the inspiratory lumen is never completelyoccluded by the airway resistance mechanisms, molded stops may befabricated in a manner that the airway may always have a slight openingfor inspiration to occur. As another option, the valve and sensingsystem may be attached to other airway devices, including an endotracheal tube, a laryngeal mask, or the like.

FIG. 44 illustrates system 800 when mask 804 is coupled to a person andthe person inhales. As shown, the inspired gases pass through resistancemechanism 808 which has been operated to increase the resistance toflow. Optionally oxygen may also be supplied to the person throughoxygen port 822. FIG. 45 illustrates when the person exhales. As shown,the expired gases pass through one-way port 824 and through expiratoryport 826.

Although system 800 has been shown with one particular type of valve, itwill be appreciated that a variety of inflow valves may be usedincluding any of those previously described. Further, FIGS. 47-53illustrate other types of inflow valves that may be used to prevent orincrease the resistance to flow during an inspiratory effort. Further,any of these inflow valves may be coupled to other mechanisms that maybe used to operate the valve to vary the flow resistance. In this way, acontroller may be used to automatically control the amount ofresistance. Further, the controller may be coupled to one or moresensors so that various physiological parameters of the person may bekept within a desired range simply by measuring the parameters and usingthose parameters to vary the amount of resistance.

FIGS. 47A and 47B illustrate an inflow valve 836 that comprises anairway 838 and a movable disk 840. Disk 840 may be moved by any type ofmechanical mechanism to occlude airway 838 as shown to increase flowresistance.

FIG. 48A and FIG. 48B illustrate another embodiment of an inflow valve842 that comprises an airway 844 and a rotatable disk 846. As shown inFIG. 48B, disk 846 may be rotated to increase the amount of flowresistance through airway 844.

FIGS. 49A and 49B illustrate an inflow valve 848 that comprises anairway 850 that is positioned between a pair of plates 852 and 854. Asshown in FIG. 49B, a rotatable cam 856 may be employed to move plate 854to compress airway 850 and thereby increase flow resistance.Conveniently, cam 856 may be rotated by a motor 858 that in turn may becontrolled by a controller in a manner similar to that previouslydescribed.

FIGS. 50A and 50B illustrate a further embodiment of an inflow valve 860that comprises an airway 862 that is positioned between two plates 864and 866. In turn, plate 866 is coupled to a threaded shaft 868 that ismovable back and forth by a stepper motor 870 that may also be coupledto a controller. In operation, stepper motor 870 is employed to moveplate 866 against airway 862 as shown in FIG. SOB to increase theresistance to flow.

FIGS. 51A and 51B illustrate an inflow valve 872 that comprises anairway 874 that is positioned between a pair of plates 876 and 878.These plates are coupled to a caliper mechanism 880 that in turn iscoupled to a lead screw 882 that is movable by a stepper motor 884. Inthis way, stepper motor 884 may be used to operate caliper mechanism 880to in turn squeeze airway 874 as shown in FIG. 51B to increase flowresistance.

FIGS. 52A and 52B illustrate an inflow valve 886 that comprises an irisoccluding mechanism 888. As shown in FIG. 52B, iris occluding mechanism888 may be operated to decrease the size of the airway and therebyincrease flow resistance.

FIGS. 53A and 53B illustrate another embodiment of an inflow valve 890that comprises an airway 892 and a rotatable arm 894 that in turn may becoupled to a stepper motor. As shown in FIG. 53B, arm 894 is rotatableover airway 892 to increase resistance to flow.

FIGS. 54A through 54C illustrate one exemplary method for treating aperson in shock. The process begins at step 900 where the treatmentsystem may be coupled to the patient's airway. For example, the systempreviously described in connection with FIG. 42 may be coupled to thepatient's face. The power is turned on as shown in step 902 and theairway resistance mechanism may be set to an open position as shown instep 904. The treatment mechanism may include various presetphysiological parameters that may initially be read to determine theperson's condition. At step 908, a determination is made as to whether abreath has been sensed based on the physiological parameters previouslyread in step 906. If no breath has been sensed, the process is reversedback to step 904 to ensure that the airway resistance mechanism is inthe open position.

If a breath has been sensed, the process proceeds to step 910 where theairway resistance mechanism is set to a preset position. This positionmay be based on the initial physiological parameters that were sensed instep 906. Further, the airway resistance may be set manually or may bedone automatically using a controller that is programmed with variouspreset positions based on measured physiological parameters. The processthen proceeds to step 912 where the physiological parameters areevaluated to determine whether the negative inspiratory pressure isacceptable as the patient inhales. If the negative inspiratory pressureis too low, the process proceeds to step 914 where the airway resistanceis increased. This may be done in an automated manner using thecontroller which operates the airway resistance mechanism to increasethe airway resistance. After the resistance has been increased, theprocess proceeds to step 916 where sensors are employed to determinewhether a breath is sensed. If not, the process reverts back to step 904where the airway resistance is moved back to its original position or toa fully open position and the process continues.

If the negative inspiratory pressure is too high, the process mayproceed to step 918 where airway resistance is reduced. A breathmeasurement is then taken in step 920 to determine whether a breath issensed. If not, the process proceeds back to step 904 where the airwayresistance mechanism may be opened. If a breath is sensed in either step920 or step 916, the process goes back to step 912 where another checkon the negative inspiratory pressure is made. Once the negativeinspiratory pressure is acceptable, the process proceeds to step 922where the respiratory rate is evaluated. If the respiratory rate isunacceptable, the process proceeds to step 924 where the airwayresistance is reduced. An evaluation as to whether a breath is sensed ismade in step 926. If no breath is sensed, the process reverts back tostep 904 where the airway resistance mechanism may be open. If a breathis sensed, the process proceeds back to step 922 where anotherevaluation of the respiratory rate is made. If the respiratory rate isacceptable, the process proceeds to step 928 and an evaluation as to theend tidal CO₂ is made. If too low, airway resistance is increased asshown in step 930 and another evaluation is made as to whether thepatient is breathing in step 932. If not, the process proceeds back tostep 904 where the airway resistance mechanism is opened. If the endtidal CO₂ is too high, the process proceeds to step 934 where the airwayresistance is reduced and the patient's breathing is again sensed atstep 936. If no breath is sensed, the process proceeds back to step 904where the airway resistance mechanism is opened. If a breath is sensedin either steps 932 or 936, the process proceeds back to step 928 wherethe end tidal CO₂ is re-evaluated. Once acceptable, the process proceedsto step 938 where the oxygen saturation is evaluated. If too low, theairway resistance may be decreased as shown in step 940 and anevaluation is made as to whether the person is breathing as shown instep 942. If not, the process proceeds back to step 904 and the airwayresistance mechanism is opened. If the oxygen saturation is acceptable,the process proceeds to step 912 so that the negative inspiratorypressure, respiratory rate, end tidal CO₂, and oxygen saturation may becontinuously monitored and the airway resistance may be modified basedon the parameters.

Hence, the method set forth in FIGS. 54A through 54C permits variousphysiological parameters to be continuously monitored and to permit theresistance to inspiratory flow to be modified so that these parametersremain within an acceptable range when treating a patient suffering fromshock. Further, as previously described, the augmentation of negativeinspiratory pressure permits increased blood flow back to the rightheart to increase the patient's blood pressure. Although shownmonitoring the various physiological parameters in a certain order, itwill be appreciated that the parameters may be monitored in other ordersas well. Further, other physiological parameters may be measured toensure that the patient remains in a stable condition when treating thepatient for shock. Optionally, the method of FIGS. 54A through 54C mayalso be used to evaluate the patient's positive end expiratory pressure.Further, similar airway resistance mechanisms may be applied to theexpiratory port and the airway resistance of the expiratory port may bevaried based on the sensed parameters. For example, the expiratorypressure may be varied to aid in the prevention of alveoli collapse(atelectasis) which may occur when the negative intrathoracic pressureis too low for a prolonged period of time.

Although the foregoing invention has been described in some detail byway of illustration and example, for purposes of clarity ofunderstanding, it will be obvious that certain changes and modificationsmay be practiced within the scope of the appended claims.

1. A method for increasing circulation in a breathing person, the methodcomprising: interfacing a valve system to the person's airway, the valvesystem being configured to decrease or prevent respiratory gas flow tothe person's lungs during at least a portion of an inhalation event,wherein the valve system is interfaced for a time period in the rangefrom about 30 seconds to about 24 hours; permitting the person to inhaleand exhale through the valve system, wherein during inhalation the valvesystem functions to produce a vacuum within the thorax to increase bloodflow back to the right heart of the person, thereby increasing cardiacoutput and blood circulation.
 2. A method as in claim 1, wherein thevalve system is incorporated into a facial mask, and further comprisingcoupling the facial mask to the person's face.
 3. A method as in claim1, wherein the valve system includes a pressure responsive inflow valve,and further comprising setting an actuating pressure of the valve to bein the range from about 0 cm H₂O to about −40 cm H₂O.
 4. A method as inclaim 1, further comprising varying the actuating pressure of the valveover time.
 5. A method as in claim 1, wherein the valve system isfurther configured to prevent or decrease exhaled gases from exiting theperson's lungs during at least a portion of an exhalation event tofurther increase blood circulation.
 6. A method as in claim 1, furthercomprising adding a supply of oxygen through the valve system tosupplement oxygen delivery to the person.
 7. A method as in claim 1,wherein the person is suffering from a disease that is related toimpaired venous blood flow.
 8. A method as in claim 1, wherein theperson is suffering from a disease resulting at least in part from poorblood circulation, and wherein the valve system functions to increaseblood circulation to treat the disease.
 9. A method as in claim 8,wherein the disease is selected from a group consisting of venous stasisulcers, deep vein thrombosis, wound healing, and lymphedema.
 10. Amethod as in claim 8, wherein the disease comprises renal failure.
 11. Amethod for increasing circulation in a breathing person, the methodcomprising: interfacing a valve system to the person's airway, the valvesystem being configured to decrease or prevent respiratory gas flow tothe person's lungs during at least a portion of an inhalation event;permitting the person to inhale and exhale through the valve system,wherein during inhalation the valve system functions to produce a vacuumwithin the thorax to increase blood flow back to the right heart of theperson, thereby increasing cardiac output and blood circulation, andwherein the person is suffering from a disease that is related toimpaired venous blood flow.
 12. A method for increasing circulation in abreathing person, the method comprising: interfacing a valve system tothe person's airway, the valve system being configured to decrease orprevent respiratory gas flow to the person's lungs during at least aportion of an inhalation event; permitting the person to inhale andexhale through the valve system, wherein during inhalation the valvesystem functions to produce a vacuum within the thorax to increase bloodflow back to the right heart of the person, thereby increasing cardiacoutput and blood circulation, wherein the person is suffering from adisease resulting at least in part from poor blood circulation, andwherein the valve system functions to increase blood circulation totreat the disease.